Science and Technology

The governing principle is that the genetic code is essentially universal, so a coding sequence taken from any organism can in principle be read by the transcription and translation machinery of any other, provided a suitable promoter and delivery vector are supplied. Taxonomic distance is a technical obstacle, not a barrier of kind.

• Statement 1 is correct and is the least demanding of the three; transfer between plant species is the oldest and commonest application, seen in herbicide tolerance and virus resistance traits moved across crop species.
• Statement 2 is correct. Animal to plant transfer is well established, the standard classroom examples being fish antifreeze protein genes introduced into plants for cold tolerance and mammalian genes expressed in plant systems for molecular farming of pharmaceutical proteins.
• Statement 3 is correct and is the most familiar of all in the Indian context: the cry genes of the soil bacterium Bacillus thuringiensis transferred into cotton and brinjal are a microorganism to higher organism transfer. All three being correct, the official answer is (d). There is no elimination route here and none is needed, since the universality of the code makes the whole set follow from a single principle.

• Statement 1 is correct. Bagasse is the fibrous residue left after cane is crushed and juice extracted, and it is burnt in the mill's own boilers to raise steam and generate power. Indian sugar mills are cogeneration units for this reason, many of them exporting surplus power to the grid, and bagasse is also a feedstock for paper and particle board.
• Statement 2 is incorrect, and this is the tested item. Molasses is the viscous residue left after sucrose crystallisation, and its uses are fermentative and nutritional: potable and industrial alcohol, ethanol, yeast, citric and acetic acid, and cattle feed. Synthetic chemical fertilizers are made from wholly different feedstocks, ammonia synthesised from natural gas or naphtha for nitrogenous fertilizers, rock phosphate for phosphatic and mined potash for potassic. The word synthetic is decisive: press mud and spent wash from distilleries are indeed returned to the field as organic manure, but that is a bio manure route, not the manufacture of a synthetic chemical fertilizer.
• Statement 3 is correct and is the basis of the Ethanol Blended Petrol Programme, molasses being the principal Indian ethanol feedstock at the time this paper was set. The official answer (c), one and three only, follows. There is no elimination route: the candidate must adjudicate statement 2 on its own, since statements 1 and 3 are both secure and the option set splits precisely on it.

Aflatoxins are secondary metabolites of filamentous fungi, principally Aspergillus flavus and Aspergillus parasiticus, which colonise groundnut, maize, cottonseed, chillies and tree nuts under warm and humid storage conditions, above roughly 25 degrees Celsius and 85 per cent relative humidity. Moulds are fungi in their filamentous growth form, so option (c) is correct. Aflatoxin B1 is a potent hepatotoxin and a Group 1 human carcinogen, acting synergistically with hepatitis B in liver cancer, and the detail in the stem about survival of cooking is accurate, the molecule being thermostable to about 250 degrees Celsius, which is why prevention at drying and storage rather than treatment at the kitchen is the whole of the control strategy.

• Option (a) is incorrect; bacteria produce their own important food toxins, the botulinum toxin of Clostridium botulinum and the enterotoxins of Staphylococcus aureus, but not aflatoxins, and the whole class name mycotoxin points to fungi.
• Option (b) is incorrect, protozoa being agents of infection rather than producers of food storage toxins.
• Option (d) is incorrect, viruses being obligate intracellular parasites with no independent metabolism, so they cannot synthesise a secondary metabolite in stored grain at all. The elimination route runs through the last of these: a candidate who holds the principle that viruses have no metabolism of their own can discard option (d) on structure alone, and the term mycotoxin then carries the rest.

• Item 1, Agaricus, is not a biofertilizer. It is the genus of the common button mushroom, a saprophytic basidiomycete grown for food on composted substrate. The fungi that do serve as biofertilizers are the mycorrhizal symbionts, Glomus and the other arbuscular mycorrhizal genera, which extend the absorptive reach of the root and mobilise phosphorus, and Agaricus forms no such association with crop roots.
• Item 2, Nostoc, is a biofertilizer and is the securest item in the set. It is a filamentous cyanobacterium with specialised heterocysts, the thick walled anaerobic cells in which nitrogenase fixes atmospheric nitrogen, and it is one of the standard blue green algal inoculants for wetland paddy alongside Anabaena, Aulosira and Tolypothrix.
• Item 3, Spirogyra, is a filamentous green alga of freshwater bodies with the characteristic helical chloroplast. It fixes no nitrogen. Its claim to the label rests on the broader sense in which algal biomass added to a paddy field contributes organic matter, and on its presence in mixed algal preparations, which is why the official key accepts it. Taking items 2 and 3, the official answer is (c). The elimination route disposes of half the option set and no more: Agaricus removes option (a) and Nostoc removes option (d), after which the choice between (b) and (c) rests wholly on Spirogyra, with no second fact available to settle it.

The governing principle is the route of transmission, and tattooing transmits disease by one route only, percutaneous inoculation of infected blood through a contaminated needle.

• Item 2, hepatitis B, qualifies and is the most efficiently transmitted of the three by this route, the virus being highly stable outside the body and infectious at very low inoculum, which is why hepatitis B and hepatitis C are the classic tattooing and unsafe injection risks.
• Item 3, HIV, qualifies, needle borne transmission being well established, though the per exposure risk is considerably lower than for hepatitis B.
• Item 1, chikungunya, does not qualify. It is an arbovirus transmitted by the bite of infected Aedes aegypti and Aedes albopictus mosquitoes, and its epidemiology is entirely vector borne; a brief viraemia exists, so transfusion associated transmission is theoretically possible, but it is not a disease transmitted by tattooing in any practical sense and is not so classified. The official answer (b) follows. The elimination route is chikungunya alone, which appears in options (a), (c) and (d), so recognising it as vector borne settles the question in one step without needing to weigh the relative risk of the other two.

• Item 1, calcium, is central and is the item no candidate should miss. Depolarisation of the sarcolemma releases calcium from the sarcoplasmic reticulum; calcium binds troponin C, which shifts tropomyosin off the myosin binding sites on actin, and cross bridge cycling follows. Without calcium there is no contraction, and the return of calcium to the reticulum is what produces relaxation.
• Item 3, sodium, is required for the event that precedes this. The action potential that travels along the motor neuron and then along the muscle fibre membrane and down the T tubules is generated by the inward sodium current through voltage gated sodium channels, so excitation contraction coupling cannot begin without sodium.
• Item 2, iron, is accepted by the official key. Its role is oxidative rather than mechanical: iron is the metal centre of haemoglobin, which delivers oxygen to the muscle, and of myoglobin, which stores it within the fibre, and it is also present in the cytochromes of the electron transport chain that regenerate the ATP consumed by the myosin head. Sustained contraction is impossible without it, which is why iron deficiency presents as muscular fatigue and weakness. Taking all three, the official answer is (d).

A harvested fruit remains metabolically alive, and its deterioration is driven by continuing respiration, which oxidises stored sugars and organic acids, releases heat and carbon dioxide, and progressively depletes the reserves that maintain tissue integrity, and by the ripening cascade that ethylene sets off. Both processes are enzyme catalysed, and the rate of an enzyme catalysed reaction falls sharply with temperature, the rule of thumb being a halving for every ten degrees Celsius of cooling. Refrigeration therefore slows respiration, delays ripening and senescence and also suppresses the growth of the spoilage fungi and bacteria that would otherwise colonise the tissue, and option (c) is correct.

• Option (a) is incorrect: darkness is incidental to cold storage and has no bearing on shelf life, harvested fruit not being photosynthetically dependent, and fruit stored in the dark at room temperature spoils on the ordinary timetable.
• Option (b) is incorrect as an explanation of what a cold chamber does. Raising carbon dioxide and lowering oxygen genuinely does extend storage life and is the basis of controlled atmosphere and modified atmosphere storage, but that is a different technology applied in addition to refrigeration, and it is not what cooling by itself achieves; the option is included precisely to catch a candidate who knows about controlled atmosphere storage and over reads the question.
• Option (d) is incorrect: high humidity is maintained in cold stores to prevent moisture loss and shrivelling, so it is a supporting condition rather than the reason, and excessive humidity encourages fungal growth. The governing principle is temperature dependence of metabolic rate.

The purpose of a ball bearing is to replace sliding friction between the shaft and its housing with rolling friction, and rolling friction is smaller by one to two orders of magnitude. The mechanism is that the hardened spheres interpose themselves between the two surfaces so that contact is reduced to a set of very small, nearly point contacts which roll rather than slide, and the relative motion is taken up by rotation of the balls instead of by shearing of the interface.

• Option (c) states this and is correct.
• Options (a) and (b) are incorrect because each asserts an increase in contact area, which would raise friction rather than reduce it and would defeat the purpose of the device.
• Option (d) fails once (c) is established. The physical qualification worth stating to a class is that classical friction between dry surfaces is independent of the apparent area of contact, which is what makes the wording of this question loose; what actually matters is the real area of contact at the asperity level and, more importantly, the change in the mode of relative motion from sliding to rolling. The examiner's phrase effective area of contact should be read as pointing at the near point contact of the rolling elements. The elimination route is direction alone: two options assert an increase and one a decrease, and friction must be reduced for the device to be useful.

The key groups together three phenomena in which what the observer sees is not what is physically there, and separates them from two in which the object is genuinely where and as it appears.

• Item 1 qualifies: the sun at the horizon subtends the same angle as at the zenith, as photography confirms, yet appears markedly larger, and the enlargement is a perceptual effect arising from the presence of intervening terrain and from the way the visual system judges distance against the apparent dome of the sky. It is a true illusion in the strict sense.
• Item 2 qualifies on the key's reading: the sun is not in fact red, and its apparent colour at dawn arises because the long slant path through the atmosphere scatters the shorter wavelengths out of the direct beam by Rayleigh scattering, leaving the transmitted light reddened.
• Item 4 qualifies on the same reading: the star does not vary in brightness, and the twinkling is scintillation produced by refraction through turbulent cells of differing density in the atmosphere, which is why planets, subtending a measurable disc, twinkle far less than point like stars.
• Item 3 does not qualify: the moon really is above the horizon at dawn whenever its phase and position place it there, and there is nothing false in the perception.
• Item 5 does not qualify: Polaris really is visible in the northern sky, standing almost on the extension of the earth's axis, which is why it appears nearly stationary while the other stars circle it. The official answer (c) follows. The elimination route is exceptionally clean and does not require the illusion category to be defined at all: items 3 and 5 are plainly real, and no option contains either of them together with the correct remainder except (c), so rejecting the two real phenomena settles the question.

Root hairs are unicellular tubular extensions of the epidermal cells of the young root, extremely fine and extremely numerous, and they are responsible for very nearly the whole of the plant's uptake of water and dissolved minerals because they multiply the absorptive surface area many times over. They are also delicate and short lived, and they are torn away when a seedling is lifted from the soil, since they are intimately bound to soil particles. The seedling therefore continues to transpire from its leaves while its capacity to absorb water has collapsed, and it wilts and often dies before new root hairs are regenerated behind the growing tip. This is exactly why transplanting is done in the evening or in overcast weather, why the seedling is watered immediately and shaded, and why nurseries raise seedlings in pots or plugs so that the root ball and its hairs are lifted intact.

• Option (c) is correct.
• Option (a) is incorrect as a general explanation, since transplanting shock occurs even into rich and well prepared soil and the failure is immediate rather than nutritional.
• Option (b) is incorrect and is close to meaningless; root hairs adhering firmly to soil is the normal and desirable condition, being how the absorptive contact is made.
• Option (d) is incorrect: leaves may be damaged incidentally, but leaf damage reduces transpiration and photosynthesis rather than causing the acute water stress that kills the seedling. The elimination route is to ask which structure is both indispensable and fragile.

• Statement 1 is correct and states the defining property of a virus. A virion consists of nucleic acid, either DNA or RNA, enclosed in a protein capsid and sometimes a lipid envelope, and it carries no ribosomes, no machinery of the citric acid cycle and no electron transport chain, so it can neither generate ATP nor synthesise protein on its own. It is metabolically inert outside a host and is an obligate intracellular parasite, which is the reason viruses sit on the border of the living and the non living.
• Statement 2 is incorrect and follows directly from statement 1. Because a virus cannot replicate without host machinery, it cannot be grown on any synthetic or cell free medium however enriched; cultivation requires living cells, in practice tissue culture, embryonated eggs or laboratory animals, and this is precisely what distinguishes viral from bacterial culture.
• Statement 3 is incorrect on the word only. Biological vectors are one route, and an important one for the arboviruses, dengue, chikungunya and Japanese encephalitis among them, but viruses are also transmitted directly by respiratory droplets and aerosols, by contact, by the faecal oral route, by blood and by vertical transmission from mother to child, as Q46 of this same paper illustrates with hepatitis B and HIV transmitted through tattooing. The official answer (a) follows. The elimination route is that statements 1 and 2 are logically inconsistent with one another, so a candidate who sees that a particle with no energy generating enzymes cannot be cultured on a lifeless medium has settled both statements from a single idea, which removes options (b) and (d) at once.

• Statement (a) is not correct and is therefore the answer. Gravity is by an enormous margin the weakest of the four. Taking the strong interaction as unity, the electromagnetic interaction is of the order of ten to the minus two, the weak interaction of the order of ten to the minus six or smaller, and gravity of the order of ten to the minus thirty nine. The comparison that fixes it is that the electrostatic repulsion between two protons exceeds their gravitational attraction by about thirty six orders of magnitude. Gravity dominates at astronomical scale for two reasons that have nothing to do with its strength: it has infinite range and, uniquely, it has only one sign of charge, so it never cancels, whereas the far stronger electromagnetic force is neutralised in bulk matter because positive and negative charges balance.
• Statement (c) is correct: the weak interaction mediates beta decay, converting a neutron into a proton with the emission of an electron and an antineutrino, and it is responsible for radioactive decays that the strong and electromagnetic interactions cannot produce, as well as for the first step of hydrogen fusion in the sun.
• Statement (d) is correct: the strong interaction binds quarks into nucleons and, in its residual form, binds nucleons to one another against the electrostatic repulsion of the protons, which is what makes the nucleus stable at all. The official answer (a) follows.

• Statement 1 is correct and is the whole significance of the particle. The Standard Model requires the carriers of the weak interaction, the W and Z bosons, to be massive, but a mass term inserted by hand destroys the gauge symmetry on which the theory rests. The Brout Englert Higgs mechanism resolves this by postulating a scalar field with a non zero vacuum expectation value which breaks the electroweak symmetry spontaneously; the gauge bosons acquire mass by interacting with this field, and the fermions acquire mass through Yukawa coupling to it, the strength of the coupling determining the mass. The Higgs boson is the quantum excitation of that field, so detecting it is the experimental confirmation that the field exists and that the mechanism is the right account of the origin of mass.
• Statement 2 is incorrect and is science fiction: teleportation of matter is not a prediction of the Standard Model or of any part of it, and quantum teleportation, which is a real laboratory technique, transfers a quantum state and not matter, requires a classical channel and moves nothing physically.
• Statement 3 is incorrect. Nuclear fission is governed by the strong and weak interactions acting on nuclei at energies of the order of millions of electron volts, and it depends on the properties of fissile nuclides, whereas the Higgs is a heavy unstable particle produced at energies of the order of hundreds of billions of electron volts with a lifetime of the order of ten to the minus twenty two seconds. There is no conceivable engineering pathway from one to the other. The official answer (a) follows. The elimination route is that statements 2 and 3 both promise a near term technology from a fundamental discovery, which is the signature of a planted falsehood in this paper's construction.

• Statement 1 is correct and states the fundamental distinction between the two routes. Photovoltaic conversion is a quantum process: a photon of energy greater than the band gap generates an electron-hole pair in a semiconductor and the built-in field of the p-n junction separates the carriers, producing current without any intermediate thermal or mechanical stage. Solar thermal conversion is a heat-engine process: concentrating collectors raise a working fluid to high temperature, and the heat is converted to work in a Rankine or Brayton cycle and thence to electricity, so it is subject to the Carnot limit in a way photovoltaics is not.
• Statement 2 is incorrect, and is the inversion of the truth. A photovoltaic cell is a direct-current device; the current flows one way across the junction, and an inverter is needed before the output can be fed to the grid. Solar thermal plants drive a conventional synchronous turbo-alternator and therefore produce alternating current natively.
• Statement 3 is incorrect. In 2014 India had a substantial and long-established photovoltaic manufacturing base in cells and modules, dating to the 1980s, while its solar thermal manufacturing capability was thin and most concentrating solar power components for the Jawaharlal Nehru National Solar Mission projects were imported. The statement reverses the position. The official answer is therefore (a).
• Statement 2 is the decisive one and is settled by physics alone, with no recall of Indian industry required: rejecting it removes (b) and (c), and statement 1 is manifestly true, which removes (d).

• Statement 3 alone is correct. Smallpox is the only human disease ever to have been eradicated. The last naturally occurring case in India was recorded in 1975, India was certified free of smallpox in 1977, and global eradication was certified by the World Health Organization in 1980 following the intensified programme built on surveillance, containment and ring vaccination.
• Statement 1 is incorrect. Diphtheria has been greatly reduced by DPT immunisation but continues to occur in India, with recurrent outbreaks in under-immunised populations; controlled is not eradicated.
• Statement 2 is incorrect. Chickenpox, caused by varicella zoster virus, remains endemic; varicella vaccine is not part of India's Universal Immunisation Programme, and because the virus establishes lifelong latency in dorsal root ganglia and reactivates as herpes zoster, it has a reservoir that makes eradication far harder than for smallpox. The official answer is (b). The governing distinction is between eradication, meaning permanent reduction of worldwide incidence to zero so that intervention can cease, elimination, meaning reduction to zero in a defined geographical area, and control. Smallpox was uniquely eradicable because it had no animal reservoir, no latent or carrier state, and a visible rash that made every case detectable.

All three are correct, so the official answer is (c). Hibernation is a state of controlled metabolic depression in which body temperature, heart rate and oxygen consumption fall far below normal, allowing an animal to survive a season when food is scarce and thermoregulation would be prohibitively expensive.

• Statement 1 is correct: temperate insectivorous bats are among the deepest hibernators known, with body temperature dropping to within a degree or two of ambient and heart rate falling from several hundred beats a minute to a handful.
• Statement 3 is correct: rodents furnish the classical laboratory models of hibernation, including the ground squirrels, marmots, hamsters and the dormouse, whose name records the habit.
• Statement 2 is correct as conventionally taught: bears den through the winter, cease feeding, urinating and defecating for months, and depress metabolic rate substantially. The elimination route is decisive and requires only one fact. Rodents are indisputable hibernators, and (c) is the only option that contains statement 3, so the item is settled without any need to adjudicate the harder question of bears.

• Statement 1 is correct. Agni-IV is a surface-to-surface ballistic missile, launched from a road-mobile transporter erector launcher.
• Statement 2 is incorrect. Agni-IV is a two-stage missile using solid propellant in both stages. Only the earliest Indian systems used liquid propellant, the Prithvi series and the first stage of Agni-I in its original configuration, and the whole direction of the Agni programme has been towards all-solid motors precisely because solid propellant permits the missile to be stored fuelled, moved on a launcher and fired at short notice, whereas a liquid-fuelled missile must be fuelled before launch and is therefore vulnerable and slow to react.
• Statement 3 is incorrect. Agni-IV has a range of the order of three thousand five hundred to four thousand kilometres with a payload of about one tonne. A figure of seven thousand five hundred kilometres exceeds even Agni-V, which is in the five thousand kilometre class, and would place the missile in the full intercontinental category, which India had not demonstrated. The official answer is therefore (a).
• Statement 2 is the decisive one and settles the item on a single principle rather than on a recalled number: the strategic logic of a survivable land-based deterrent requires solid propellant, and a candidate who holds that principle rejects statement 2 without hesitation, which removes (b) and (d), and statement 1 is beyond argument, which removes nothing but confirms (a) once statement 3 is rejected on range.

• Option (b) is correct. Guar gum is a galactomannan polysaccharide obtained from the endosperm of the cluster bean seed. In water it hydrates to give very high viscosity at low concentration, and it is cross-linked with borate or metal ions to form the gel that carries proppant, usually sand, into the fractures opened by hydraulic fracturing, holding them apart after pressure is released; a breaker is then used to degrade the gel so that the gas can flow. The expansion of shale gas production in the United States accordingly generated an enormous derived demand for Indian guar, which is grown chiefly in Rajasthan, Haryana and Gujarat, and prices rose sharply in 2012.
• Option (a) is incorrect: the commercial product of the seed is the gum from the endosperm, not an oil, and biodegradable plastics are made from starch, polylactic acid and polyhydroxyalkanoates.
• Option (c) is incorrect: no antihistamine property of the leaf is the reason for the crop's new significance.
• Option (d) is incorrect: guar is not a biodiesel feedstock, that role in India belonging to jatropha, pongamia and used cooking oil. The stem itself supplies the route, since it says the recent significance is new and commercial, and only option (b) names an industrial demand that arose recently.

• Statement 1 is correct. Neem oil and neem seed kernel extract contain azadirachtin and related limonoids, which act as antifeedants, oviposition deterrents and insect growth regulators, disrupting moulting by interfering with ecdysteroid function; they are effective against a wide range of chewing and sucking insects and against mites, and the mode of action makes resistance slow to develop.
• Statement 3 is correct. Neem oil and its fractions are used in antiseptic, antifungal and dermatological preparations, and nimbidin and related compounds are the subject of a large pharmacological literature. The key treats statement 2 as incorrect and answers (c). The rejection has to rest on the statement being compound: it asserts both biofuel manufacture and hospital detergent manufacture, and if either limb fails the whole fails. On the key's reading, neem seed oil as a biodiesel feedstock is a laboratory and pilot proposition rather than a manufacturing reality, and hospital detergent is not a recognised neem product line.
• Statements 1 and 3 are both secure, so eliminating either is impossible; the item is decided wholly on statement 2, between (c) and (d), with (a) and (b) removed by the security of statements 3 and 1 respectively.

• Option (b) is correct on the reading the examiner intends. Photosynthesis takes radiant energy, which is available and unstored, and converts it into chemical energy locked in the bonds of carbohydrate, where it remains stored until released by respiration. The light reactions in the thylakoid membrane use photon energy to drive water oxidation and electron transport, generating ATP and NADPH, and the carbon fixation reactions in the stroma use those to reduce carbon dioxide to triose phosphate. The direction of energy flow is from an available form to a stored form, which is what the option asserts.
• Option (a) is incorrect because it reverses that direction and describes the release of stored energy, which is respiration.
• Option (c) is incorrect and describes aerobic respiration precisely, the oxidation of food to carbon dioxide and water.
• Option (d) is incorrect and describes the gas exchange of respiration, whereas photosynthesis takes in carbon dioxide and releases oxygen; a candidate who fixes the gas exchange of the two processes disposes of (c) and (d) together. The item then reduces to (a) against (b) and is settled by the direction of energy conversion.

All three are correct, so the official answer is (d). A biometric modality is usable for identification if the underlying trait is sufficiently distinctive between individuals, sufficiently stable over time, universally present and practically measurable.

• Statement 1 is correct: the iris has a highly complex trabecular texture fixed in the first years of life and different even between the two eyes of one person and between identical twins, and iris recognition is among the most accurate modalities in use, which is why Aadhaar captures it.
• Statement 2 is correct: retinal scanning maps the pattern of blood vessels at the back of the eye, is extremely accurate, but requires close and cooperative presentation, so it is used in high-security applications rather than in mass enrolment; it is distinct from iris scanning, and the item is testing whether the candidate treats the two as the same thing.
• Statement 3 is correct: voice recognition uses vocal tract and behavioural characteristics and is a recognised modality, weaker than the ocular ones because voice varies with health, age and emotional state, but it is nonetheless in use, notably in telephone banking. The item asks what can be used, not what is most accurate, so the lower reliability of voice does not exclude it.

• Statements 1 and 3 are correct and statement 2 is incorrect, so the official answer is (c).
• Statement 1 is correct by definition: vegetative propagation proceeds by mitosis from somatic tissue of a single parent, so the progeny are genetically identical to the parent and to one another, which is what a clone is, and this is precisely why it is used for fruit crops where a desirable genotype must be preserved unchanged.
• Statement 3 is correct: because propagation does not depend on flowering, pollination or seed set, it is not confined to a reproductive season, and cuttings, layering, budding and grafting can be carried out over much of the year subject only to the physiological condition of the stock and scion.
• Statement 2 is incorrect and is the pivot of the item. Vegetative propagation perpetuates viruses rather than eliminating them, because most plant viruses are systemic and move through the vascular system, so any cutting, tuber, sucker or scion taken from an infected plant carries the infection with it; this is why virus accumulation over successive vegetative generations is a standing problem in potato, sugarcane, banana and citrus. The technique that does eliminate virus is meristem tip culture, and the reason it works is instructive: the apical meristem has no differentiated vascular tissue, its cells divide rapidly and outpace viral movement, and a sufficiently small excised tip is therefore usually virus-free.

• Pair 1 is incorrectly matched. Cassini-Huygens was a joint NASA, European Space Agency and Italian Space Agency mission to Saturn, not Venus; the Cassini orbiter entered Saturn orbit in 2004 and the Huygens probe descended to the surface of Titan in January 2005, the first landing in the outer solar system. Cassini did make two gravity-assist flybys of Venus on the way out, which is presumably where the distractor comes from, but a flyby en route is not the purpose of a mission.
• Pair 2 is correctly matched. MESSENGER, standing for Mercury Surface, Space Environment, Geochemistry and Ranging, entered Mercury orbit in March 2011 and mapped the planet in full, its most reported finding being water ice in permanently shadowed polar craters.
• Pair 3 is correctly matched. Voyager 1 and 2 were launched in 1977 and conducted the grand tour of the outer planets, Voyager 2 remaining the only spacecraft to have visited Uranus and Neptune. The official answer is (b).
• Pair 1 is the decisive one and Cassini's association with Saturn and Titan is secure enough that rejecting it removes (a), (c) and (d) in a single step.

• Statement 3 alone is correct, so the official answer is (b). The test for a chemical change is whether new substances with different chemical identities are formed, which requires the breaking and making of chemical bonds, and whether the change is readily reversible by physical means.
• Statement 1 is a physical change: crystallisation of sodium chloride from solution rearranges ions from the dissolved state into a lattice, but the substance remains sodium chloride throughout and dissolving the crystals restores the solution.
• Statement 2 is a physical change: melting of ice is a phase transition in which hydrogen bonds between water molecules are disrupted but no covalent bond within a water molecule is broken, so the substance is water before and after and freezing reverses it.
• Statement 3 is a chemical change: souring occurs because lactic acid bacteria ferment lactose to lactic acid, a different compound with different properties, and the fall in pH denatures casein and curdles the milk. Nothing can restore the original milk. The item is answered by applying the single criterion of whether a new substance is produced, and it is worth noting that the enthalpy involved in a phase change is comparatively small precisely because intermolecular rather than intramolecular forces are being overcome.

A transgenic crop is one into which a gene from outside the sexually compatible gene pool has been introduced, so the test for each item is whether it is a route by which foreign DNA is put into and expressed in a plant.

• Statement 1 is incorrect. Budding and grafting join the tissues of two plants so that they grow as one, but the scion and the stock retain their own genomes and no genetic material is transferred or recombined; it is a horticultural propagation technique of great antiquity and has nothing to do with transformation.
• Statement 3 is correct. Gene silencing, whether by antisense RNA or by RNA interference through the introduction of a construct producing double-stranded RNA, is achieved by inserting an engineered construct into the plant genome, so the resulting plant is transgenic; the delayed-ripening tomato and virus-resistant papaya are the standard examples, and RNA interference constructs against insect target genes are a current line of work.
• Statement 2 is treated as correct by the key. In its classical form cytoplasmic male sterility is a naturally occurring mitochondrial trait used in conventional hybrid seed production and involves no transgene at all, so the key must rest on the engineered male sterility systems, of which the barnase and barstar system is the leading example, where a ribonuclease gene under a tapetum-specific promoter is inserted to abolish pollen production and a matching inhibitor gene restores fertility in the hybrid. The official answer is (b).
• Statement 1 is the only one that can be rejected without hesitation, and doing so removes (a) and (c), after which the item turns on statement 2 between (b) and (d).

All three are correct, so the official answer is (d).

• Statement 1 is correct and is the largest industrial use of the grain: the maize kernel is roughly seventy per cent starch by weight, and wet milling separates it into starch, germ, gluten and fibre, the starch going on to modified starches, dextrose, high fructose syrup and a large range of food and industrial products.
• Statement 2 is correct: maize germ, separated in milling, yields corn oil, and any triglyceride oil can be transesterified with a short-chain alcohol to give fatty acid methyl esters, which is biodiesel. Whether it is economic to use an edible oil for the purpose is a separate question from whether it is technically a feedstock, and the statement claims only the latter.
• Statement 3 is correct: the starch is hydrolysed to fermentable sugars and fermented by yeast, which is the basis both of maize-based spirits such as bourbon and of fuel ethanol, the two differing in purification rather than in the underlying process. The item is answered by recognising maize as a starch crop and then reasoning that a starch crop with an oil-bearing germ necessarily supports all three uses, so no recall of an industrial list is needed.

• Pairs 1 and 2 are correctly matched and pair 3 is not, so the official answer is (a).
• Pair 1 is correct: ascorbic acid is a cofactor for the hydroxylation of proline and lysine residues in procollagen, and without that hydroxylation the collagen triple helix is unstable, which is why deficiency produces the bleeding gums, poor wound healing, loose teeth and perifollicular haemorrhages of scurvy.
• Pair 2 is correct: vitamin D is required for the absorption of calcium from the gut and for normal mineralisation of the growing bone, and deficiency in children produces rickets, with bowing of the long bones and costochondral beading, the corresponding adult condition being osteomalacia.
• Pair 3 is incorrect: night blindness is the deficiency disease of vitamin A, because retinal, the aldehyde form of the vitamin, combines with opsin to form rhodopsin, the pigment of the rod cells that mediates vision in dim light, and its absence progresses through nyctalopia to xerophthalmia and keratomalacia. Vitamin E is an antioxidant tocopherol whose deficiency, uncommon in humans, presents with haemolysis and neurological signs. The item is decided on pair 3, and the vitamin A association with vision is among the most secure facts in the syllabus, so its rejection removes (b), (c) and (d) together.

• Statement 1 is correct. The National Innovation Foundation, set up at Ahmedabad in 2000, is an autonomous body of the Department of Science and Technology.
• Statement 2 is incorrect and inverts the Foundation's purpose. NIF exists to scout, document, value add and protect grassroots technological innovation and outstanding traditional knowledge developed by people in the unaided or informal sector, typically farmers, artisans and school children; it is a grassroots innovation body, not a frontier research body, and its work is not built on collaboration with foreign scientific institutions. The official answer (a) follows.
• Options (b) and (d) are excluded by statement 1 and option (c) by statement 2. The elimination route is the mismatch between the word innovation, which in Indian science administration attaches to grassroots and translational work, and the language of advanced research in premier institutions, which describes bodies such as SERB or the international bilateral programmes.

• Option (b) is correct. The West African Ebola epidemic of 2014 to 2016, the largest on record, was centred on Guinea, where the index case was traced to Meliandou in December 2013, and on the neighbouring states of Liberia and Sierra Leone; the World Health Organization declared it a Public Health Emergency of International Concern in August 2014.
• Option (a) is wrong: Syria and Jordan were in the news for the civil war and the refugee inflow.
• Option (c) is wrong: the Philippines had earlier reported Reston ebolavirus in macaques, which does not cause human disease, but no human outbreak.
• Option (d) is wrong: the Caribbean states listed had no Ebola cases, and the 2014 outbreak in that region was chikungunya. Elimination route: Ebola virus disease is a zoonosis of Central and West African forest ecosystems with fruit bats as the reservoir, so only the African option can be right.

• Statement 1 is correct. Nanoscale carriers such as liposomes, polymeric micelles, dendrimers and gold nanoparticles carry a drug payload to a chosen site, by passive accumulation through the enhanced permeability and retention effect of leaky tumour vasculature and by active targeting through ligands that bind receptors overexpressed on the target cell. Doxorubicin in liposomal form was already in clinical use well before this paper.
• Statement 2 is correct. Non-viral nanoparticle vectors, principally lipid and polymeric nanoparticles, are a principal route for delivering nucleic acids into cells, the delivery problem rather than the editing chemistry being the main obstacle in gene therapy. The official answer (c) follows, and there is no elimination route, both statements having to be judged independently.

• Statement 1 is correct. The IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station instruments a cubic kilometre of Antarctic ice with 5160 digital optical modules on 86 strings, making it the largest neutrino detector built. It works by detecting the Cherenkov light emitted when a neutrino interaction produces a relativistic charged secondary in the ice, the ice serving as both target mass and detecting medium.
• Statement 3 is correct: the strings hang between about 1450 and 2450 metres below the surface, deep enough for the ice to be bubble free and optically clear, with the IceTop array at the surface.
• Statement 2 is treated as correct by the key. IceCube's primary mission is high energy astrophysical neutrino astronomy, but indirect dark matter search is a published part of its programme, since neutralino or WIMP annihilation in the Sun, the Earth's core or the galactic centre would produce a neutrino excess from those directions, and IceCube has set some of the strongest limits on spin dependent WIMP-proton cross sections. The official answer (d) follows. Elimination route: statements 1 and 3 are secure, which removes (a) and (b) at once, so the item reduces to a judgement on statement 2.

• Statement 1 is correct. Near Field Communication is a short range contactless technology operating at 13.56 megahertz, in which an initiator generates an alternating magnetic field and the target either powers itself from that field, in passive mode, or generates its own, in active mode. The coupling is inductive and takes place in the near field of the antenna, which is what the name records.
• Statement 2 is incorrect and is the whole point of the item: the working range of NFC is about four centimetres, deliberately so, because proximity is itself the security model. A metre would be the range of Bluetooth Low Energy or of a passive ultra high frequency RFID tag, not of NFC.
• Statement 3 is correct: NFC defines only the link, and application layers built on it, such as EMV contactless payment or secure element based ticketing, routinely apply encryption and cryptographic authentication to the payload. The official answer (c) follows. Elimination route: knowing the four centimetre range removes options (a) and (d) at once, and statement 1 is secure, which removes (b). The governing principle is that near field means the reactive region within a fraction of a wavelength of the antenna, which for 13.56 megahertz is centimetres, not metres.

• Option (c) is correct. The Goldilocks Zone, more formally the circumstellar habitable zone, is the range of orbital distances from a star within which the stellar flux received by a planet would allow liquid water to persist on its surface given adequate atmospheric pressure, neither so close that water is lost to a runaway greenhouse nor so far that it freezes. The name is from the fairy tale, the porridge being neither too hot nor too cold. Its boundaries depend on stellar luminosity and temperature, so the zone lies closer in for a cool M dwarf and further out for a hotter star, and it is the standard criterion applied when a transiting exoplanet is reported as potentially Earth like.
• Option (a) is wrong and inverts the concept, which concerns distance from a star, not altitude above a planet.
• Option (b) is wrong: shale gas occurrence is governed by the thermal maturity window for hydrocarbon generation, a different idea although also a zone defined by temperature.
• Option (d) is wrong: there is no such usage in meteoritics. Elimination route: the term recurs in exoplanet reporting, and only option (c) concerns other planets.

• Option (d) is correct. H1N1 designates an influenza A subtype named for its surface glycoproteins, haemagglutinin type one and neuraminidase type one; the strain that caused the 2009 pandemic was a reassortant of swine, avian and human influenza genes and was accordingly called swine flu.
• Option (b) is the trap: avian influenza is also an influenza A virus, but the strains of concern carry different subtype designations, principally H5N1 and H7N9, and the H and N numbers are exactly what separate the two diseases.
• Option (a) is wrong: AIDS is caused by the human immunodeficiency virus, a retrovirus with a wholly different genome and mode of transmission.
• Option (c) is wrong: dengue is caused by a flavivirus transmitted by Aedes aegypti. The elimination route is that only two options name influenza at all, and the subtype numbering settles the choice between them. The point worth teaching is that influenza's segmented genome permits reassortment when two strains infect the same host, which is why pigs, susceptible to both avian and human strains, act as a mixing vessel and why new pandemic subtypes emerge from them.

• Statement 1 is correct. A hydrogen fuel cell oxidises hydrogen electrochemically rather than by combustion: hydrogen is oxidised at the anode, the electrons travel through the external circuit, and at the cathode oxygen combines with them and with the protons that have crossed the electrolyte to form water. Since the free energy change is not fully converted to electrical work, the balance appears as heat, so water and heat are the only by-products, and the absence of carbon in the fuel is why there is no carbon dioxide.
• Statement 2 is incorrect. Fuel cells scale across the whole range, from megawatt stationary installations down to portable units; direct methanol fuel cells were developed precisely for laptops and handheld devices, and the statement's restriction is false.
• Statement 3 is incorrect and is the cleanest elimination in the item. A fuel cell is an electrochemical cell and produces direct current by its nature, since the electrode reactions fix the polarity; an inverter must be added to supply alternating current to a grid or a building. The official answer (a) follows. Elimination route: the direct current point alone removes options (b), (c) and (d), so a candidate secure on that single fact answers the item without judging the other two statements.

• Statement 1 is correct. LiFi, or Light Fidelity, is visible light communication: data is encoded by modulating the intensity of an LED source at frequencies far above the flicker fusion threshold of the human eye, and recovered by a photodetector. The carrier is light rather than radio frequency electromagnetic radiation, which is the whole point of the technology.
• Statement 2 is also correct. LiFi is wireless, since no physical conductor carries the signal, and the visible light band offers roughly ten thousand times the spectral width of the radio frequency band, which is what permits the very high demonstrated data rates. Laboratory demonstrations before the paper had already reported speeds an order of magnitude above contemporary WiFi. Both statements being correct, the answer is (c).
• Option (d) is untenable once the name itself is decoded, and (a) and (b) each require rejecting one of two propositions that follow directly from the physics. The one nuance a candidate should hold is that LiFi requires line of sight and does not penetrate opaque barriers, but the statement claims only that it is wireless, which is true, so this limitation does not falsify it.

Neem coating works through the nitrification-inhibiting action of neem's triterpenoids, chiefly azadirachtin and related limonoids, which suppress the ammonia-oxidising bacteria that convert ammonium to nitrate. The practical effect at field level is that urea hydrolyses and becomes plant-available more slowly, so nitrogen release is spread across the crop's uptake period rather than flushed in a pulse. That reduces leaching and volatilisation losses, raises nitrogen use efficiency and, incidentally, makes the urea unpalatable for diversion to industrial uses.

• Option (b) captures this and is correct.
• Option (a) inverts the mechanism: neem does not increase microbial nitrogen fixation, it inhibits nitrifying microorganisms, and in any event fixation converts atmospheric nitrogen and is irrelevant to applied urea.
• Option (c) is wrong on an absolute qualifier: slowing nitrification reduces nitrous oxide emissions from fertilised fields but cannot eliminate them, and 'not at all' is untenable for any agricultural practice.
• Option (d) is a straightforward fabrication, neem coating being neither a weedicide nor crop-specific. The elimination route is that (c) and (d) fail on their own terms without any knowledge of neem chemistry, leaving a choice between two microbiological claims of opposite sign.

The suffix -ome denotes the complete complement of a class of molecules in a cell or organism: the genome is the full set of DNA, the proteome the full set of proteins, the metabolome the full set of metabolites. The transcriptome, correspondingly, is the full set of RNA transcripts, in the usual usage the messenger RNA molecules expressed by a cell, tissue or organism at a given time. Its scientific interest lies in the fact that unlike the genome, which is essentially fixed, the transcriptome varies with cell type, developmental stage and environmental condition, so it reports which genes are actually being expressed rather than which are merely present. Hence (b).

• Option (a) describes nucleases such as Cas9, ZFNs and TALENs, which belong to genome editing and are not a transcript population at all.
• Option (c) confuses the object with its explanation: a description of a mechanism is not a molecular complement.
• Option (d) describes mutagenesis, which concerns changes to the DNA sequence rather than the RNA output. The elimination route is entirely morphological: only one option names a complete set of molecules, which is what the -ome construction requires, so a candidate who parses the word correctly needs no bioinformatics.

• Statement 1 is correct. The Regulations require a complete list of ingredients in descending order of composition by weight or volume at the time of manufacture, and additives must be declared by class name together with the specific name or the recognised international numerical identifier.
• Statement 2 is correct. Nutritional information is a mandatory declaration on the label, covering energy value and the amounts of protein, carbohydrate and fat per hundred grams or hundred millilitres or per serving.
• Statement 3 is incorrect and is the eliminating statement. Nothing in the Regulations requires a manufacturer to reproduce recommendations of the medical profession about possible allergic reactions; what the law imposes is a declaration of the ingredients themselves, from which an allergic consumer may draw the inference, and any medical advisory would in any event be a matter for professional bodies rather than a labelling obligation.
• Statement 4 is correct and is distinctively Indian: the green filled circle in a green square for vegetarian food and the corresponding brown or red mark for non-vegetarian food are mandatory on the principal display panel. Hence 1, 2 and 4, giving (c).
• Statement 3 is implausible on its face, which removes (a) and (b) at once, leaving (c) against (d) to turn on the nutrition declaration alone.

INS Astradharini, commissioned in October 2015, is a torpedo launch and recovery vessel, indigenously designed and built to support the trials of underwater weapons and sonar systems developed by the Naval Science and Technological Laboratory at Visakhapatnam. She replaced the older Astravahini and is notable for a catamaran hull form that gives stability during launch and recovery operations. Hence (c).

• Option (a) is wrong: amphibious warfare ships of the Indian Navy are the landing platform dock and landing ship tank classes, of which INS Jalashwa is the best known.
• Option (b) is wrong: India's nuclear-powered submarines are the Arihant class and the leased Chakra, and a trials support vessel is not a submarine at all.
• Option (d) is wrong for a further reason worth stating plainly, that India has never operated a nuclear-powered aircraft carrier; Vikramaditya and the later Vikrant are conventionally powered. The name itself supplies a partial route, astra denoting a weapon and dharini a bearer or holder, which points to a weapon-carrying auxiliary rather than a combatant.

Greased Lightning-10 is a battery-powered, remotely piloted tilt-wing demonstrator built at NASA's Langley Research Center, with ten electric motors distributed along the wing and tail. Its significance is that it achieved the full transition from vertical take-off, in the manner of a helicopter, to efficient horizontal wing-borne flight, which is the hard problem in distributed electric propulsion and the technical ancestor of the urban air mobility designs that followed. Hence (a).

• Option (b) is a distractor built on solar aviation, the salient project of the period being Solar Impulse 2, which was Swiss rather than Japanese and was circumnavigating the globe while this paper was set.
• Option (c) misattributes it to Chinese space astronomy.
• Option (d) is the most tempting for an Indian candidate, since ISRO flew its Reusable Launch Vehicle Technology Demonstrator in May 2016, weeks before the exam, but that vehicle carried no such name. The elimination route is weak; the item rewards having read the specific report.

All three are correct.

• Statement 1: viruses infecting bacteria are bacteriophages, among the best studied entities in molecular biology; T4, lambda and M13 are standard laboratory organisms, and phage biology gave us restriction enzymes and, more recently, the CRISPR system, which is a bacterial defence against phage.
• Statement 2: viruses infecting fungi are mycoviruses, mostly double-stranded RNA viruses transmitted by hyphal anastomosis and sporulation rather than by an extracellular route; the best known is the hypovirus of Cryphonectria parasitica, which attenuates the virulence of the chestnut blight fungus and has been used as a biocontrol agent.
• Statement 3: plant viruses are numerous and agriculturally serious, tobacco mosaic virus being the first virus ever characterised, and the group includes cassava mosaic, banana bunchy top and the geminiviruses. Hence (d).
• Options (a), (b) and (c) each exclude a genuine host group. The governing principle, and the elimination route for a candidate who has never met a mycovirus, is that viruses are obligate intracellular parasites of cells as such, and there is no reason in principle why any cellular life form should be exempt; archaea have their own viruses too. Fungi are the only statement likely to give pause, so the item is moderate rather than easy.

ITER, under construction at Cadarache in France, is a collaboration of the European Union, India, Japan, China, Russia, South Korea and the United States, building a tokamak intended to demonstrate that a burning deuterium-tritium plasma can produce ten times the power injected to heat it. Its purpose is to establish the scientific and engineering feasibility of fusion as an energy source, and India's participation, through the Institute for Plasma Research, brings both technology and eventual access to the design knowledge. If the experiment succeeds, what India gains is the capability to build fusion reactors, giving (d).

• Option (a) confuses fuel cycles: thorium belongs to fission, and India's thorium ambitions run through the three-stage programme and the Advanced Heavy Water Reactor, not through ITER.
• Option (b) is unrelated to nuclear physics of any kind.
• Option (c) commits the same category error in the opposite direction, since success in magnetic confinement fusion tells one nothing about the efficiency of fission reactors, the two processes being physically distinct. The elimination route is complete once the candidate holds fission and fusion apart, since three of the four options describe fission or non-nuclear outcomes.

• Statement 1 is incorrect. Space-based astronomical observatories have been flown by a considerable number of space powers besides the United States and Russia: Japan's X-ray series from Hakucho through Suzaku and Hitomi, the European Space Agency's XMM-Newton, INTEGRAL, Herschel and Planck, Italy's BeppoSAX and AGILE, China's later Insight-HXMT, and others. India was the sixth or so entrant, not the third.
• Statement 2 is incorrect on both figures. AstroSat has a lift-off mass of about 1,513 kilograms, not 2,000, and was placed in a near-equatorial low Earth orbit at roughly 650 kilometres, not 1,650. The 650 kilometre altitude and the six degree inclination were chosen deliberately to keep the spacecraft below the inner radiation belt and out of the South Atlantic Anomaly for as much of each orbit as possible, since charged particle background would otherwise swamp the X-ray detectors. Both statements being false, the answer is (d).
• Options (a), (b) and (c) each require accepting one of them. The exclusivity claim in statement 1 should trigger the same suspicion as any universal or unique claim in Prelims.

• Statement 1 is correct: Mangalyaan is the popular name of the Mars Orbiter Mission, launched in November 2013 and inserted into Mars orbit on 24 September 2014.
• Statement 2 is incorrect and is the eliminating statement. India was not the second entity to orbit Mars after the United States. The Soviet Union achieved Mars orbit with Mars 2 and Mars 3 in 1971, and the European Space Agency's Mars Express has been in orbit since 2003, so India was the fourth.
• Statement 3 is correct: India is the only country to have succeeded in placing a spacecraft in Mars orbit at its first attempt. The Soviet Union, the United States, Japan and the European Space Agency all suffered failures before or during their early Mars campaigns, and the historic failure rate of Mars missions is roughly one in two, which is what makes the achievement notable. Hence 1 and 3, giving (c).
• Options (a), (b) and (d) each mishandle statement 2. The elimination route is available to anyone who recalls the Soviet Mars programme, and the internal tension in the question is itself a clue: statements 2 and 3 make different exclusivity claims about the same mission, and only one can carry the distinction.

• Statement 1 is correct. Zika virus is a flavivirus transmitted principally by Aedes aegypti, with Aedes albopictus as a secondary vector. Aedes aegypti is the same day biting, container breeding, urban adapted mosquito that transmits dengue, chikungunya and yellow fever, which is why the four diseases share a geography and why vector control measures against one serve against all.
• Statement 2 is correct. Zika is the only mosquito borne flavivirus for which sustained sexual transmission is documented. The virus persists in semen far longer than in blood, and transmission from male to female, female to male and male to male partners has all been recorded, which is why WHO guidance during the epidemic addressed abstinence or protected intercourse and deferral of conception for returning travellers. Both statements standing, the official answer (c) follows. There is no elimination route, but neither statement is obscure, both having been central to the public health messaging of the 2015 and 2016 epidemic. Teaching point worth carrying: the vertical transmission route, from mother to foetus, producing congenital Zika syndrome with microcephaly, is the third route and is the one that made the outbreak a public health emergency.

• Statement 1 is correct. BIS certification is voluntary as a general rule, but a schedule of products is brought under mandatory certification by orders issued in the interest of public health, safety or consumer protection, and pneumatic tyres and tubes for automotive vehicles have long been on that list.
• Statement 2 is incorrect and is the eliminating statement. AGMARK is a wholly Indian certification mark for agricultural produce, issued under the Agricultural Produce (Grading and Marking) Act, 1937 and administered by the Directorate of Marketing and Inspection under the Ministry of Agriculture and Farmers Welfare, covering commodities such as ghee, honey, spices, edible oils and pulses. The Food and Agriculture Organisation is a specialised agency of the United Nations engaged in standard setting through Codex Alimentarius jointly with the WHO, but it issues no product certification mark of this kind and certainly not an Indian one. The syllable 'AG' invites the misreading, and the presence of a UN agency name is the trap. Rejecting statement 2 eliminates (b) and (c); statement 1 then decides between (a) and (d). Governing principle: an Indian conformity mark is issued under an Indian statute by an Indian authority. BIS under the Bureau of Indian Standards Act, AGMARK under the 1937 Act, FSSAI licensing under the Food Safety and Standards Act, and Hallmarking by BIS. No international body issues any of them.

Both statements are correct.

• Statement 1 is correct: the Policy, approved in May 2016, expressly reaffirms India's commitment to the Doha Declaration on the TRIPS Agreement and Public Health and to the flexibilities available within TRIPS, and this reaffirmation was the politically significant element of the document, since it signalled that compulsory licensing under section 84 and the exclusion of incremental innovation under section 3(d) of the Patents Act would be retained notwithstanding sustained external pressure, particularly through the United States Special 301 process.
• Statement 2 is correct: the Policy designates the Department of Industrial Policy and Promotion, then under the Ministry of Commerce and Industry, as the nodal department to coordinate, guide and oversee implementation, and the Cell for IPR Promotion and Management was created under it for that purpose. The word 'regulating' is loosely used, since the actual grant of rights is made by the Controller General of Patents, Designs and Trade Marks and copyright administration was itself transferred to DIPP from the Ministry of Human Resource Development in 2016, but the nodal coordinating role is accurately stated. Both statements standing, the official answer (c) follows.

Both statements are correct.

• Statement 1 is correct: the Quality Council of India was established in 1997 as a non profit autonomous body registered under the Societies Registration Act, jointly by the Government of India, acting through the then Department of Industrial Policy and Promotion, and the three apex industry associations, ASSOCHAM, CII and FICCI. Its governing council is accordingly drawn from government, industry and other stakeholders in equal measure, and it is this joint parentage that distinguishes it from a statutory regulator such as BIS.
• Statement 2 is correct: the Chairman of QCI is appointed by the Prime Minister on the recommendations of the industry to the Government, which is the arrangement recorded in the Council's own constitution and is the second consequence of the joint public and private character of the body. The item is difficult because there is no elimination route and statement 2 in particular is not covered by any standard preparation source; a well prepared candidate would recognise QCI as the national accreditation body and would probably accept statement 1, but would be guessing on statement 2. Teaching point: QCI operates the accreditation boards, NABL for laboratories, NABH for hospitals and NABCB for certification bodies, and it accredits the accreditors rather than certifying products, which is the distinction from BIS.

• Option (a) is correct, and the item is solved by recognising that all four terms belong to fundamental physics and cosmology. The event horizon is the boundary surrounding a black hole beyond which no signal can escape to a distant observer, its radius for a non rotating body being the Schwarzschild radius. A singularity is the point predicted by general relativity at which curvature and density diverge, arising both at the centre of a black hole and at the initial state of the Universe. String theory is the programme that replaces point particles with one dimensional extended objects in an attempt to reconcile general relativity with quantum mechanics. The Standard Model is the quantum field theoretic account of the electromagnetic, weak and strong interactions and of the known fundamental particles.
• Options (b) and (c) are wrong because eclipses and satellite injection are problems in classical celestial mechanics and orbital dynamics, requiring nothing beyond Newtonian gravitation and involving none of these four concepts.
• Option (d) is wrong because the origin and evolution of life belongs to biology and biochemistry, and shares no vocabulary with any of the four. Elimination route: any single one of the four terms, correctly located, disposes of all three wrong options at once, so no candidate needs all four. Governing principle: identify the discipline to which a term cluster belongs before attempting to define the terms.

All three uses are established and the official answer (d) follows.

• Statement 1 is correct: sequencing identifies molecular markers, single nucleotide polymorphisms and quantitative trait loci linked to traits such as disease resistance and drought tolerance, which is the foundation of marker assisted selection.
• Statement 2 is correct and follows directly from statement 1: conventional breeding requires each generation to be grown to maturity and phenotyped, whereas marker assisted and genomic selection allow a breeder to screen seedlings at the DNA level and discard unwanted genotypes before field evaluation, and to track a recessive or difficult to phenotype trait through backcrosses, compressing the breeding cycle substantially.
• Statement 3 is correct: sequencing both host and pathogen genomes allows resistance genes to be matched against pathogen effector genes, which is how the gene for gene relationship is now investigated, and permits pathogen races to be tracked as they overcome deployed resistance. Since no statement can be rejected, there is no elimination route, but the item is easy because statement 2 follows logically from statement 1 and statement 3 is a natural extension, so a candidate who accepts the first accepts all three. Governing principle: sequencing yields information, and every legitimate application is an application of information, whether to selection, to acceleration of breeding or to the analysis of interaction.

All three pairs are correctly matched, so the official answer (d) follows.

• Pair 1 is correct. Lead occurs in lipstick as a contaminant of the mineral pigments and colour additives rather than as an intentional ingredient, and surveys by regulators including the United States Food and Drug Administration have detected it at trace levels across a large majority of tested brands; the concern is cumulative exposure through ingestion, lead being a neurotoxin with no established safe threshold.
• Pair 2 is correct. Brominated vegetable oil was used as an emulsifier in citrus flavoured soft drinks, its function being to keep the flavour oils, which are less dense than water, evenly dispersed rather than separating to the surface; the bromine raises the density of the oil to match the beverage. It is controversial on account of bromine accumulation in tissue, and has been progressively withdrawn and prohibited in several jurisdictions.
• Pair 3 is correct. Monosodium glutamate, the sodium salt of glutamic acid, is used as an umami flavour enhancer and is strongly associated with Chinese restaurant cooking, the reported symptom cluster having historically been named after it, though controlled studies have not reproduced the effect consistently and major food safety authorities regard it as generally safe. Since no pair can be rejected there is no elimination route, and a candidate must know each independently. Note that the stem is carefully worded as 'unwanted or controversial' and 'likely to be found in', which is a lower threshold than harm or intentional addition, and pair 3 in particular satisfies the stem only on that reading, monosodium glutamate being an intentional and lawful ingredient whose controversy is largely popular rather than toxicological.

All three are correct and the official answer (c) follows. The common cause of all three advantages is structural and is worth stating first: an OLED is an emissive device, in which each organic pixel generates its own light when charge carriers recombine in the organic layer, whereas a liquid crystal display is transmissive and merely shutters light from a separate backlight unit. Removing the backlight removes a rigid, bulky and opaque component, and everything else follows.

• Statement 1 is correct: the organic layers are deposited at low temperature and are thin, so they can be laid on flexible plastic or metal foil substrates, which the glass panel and rigid backlight assembly of a liquid crystal display cannot accommodate.
• Statement 2 is correct and is a direct consequence of statement 1, roll up and conformable displays including textile integrated ones having been demonstrated.
• Statement 3 is correct: with no opaque backlight behind them, transparent OLED panels can be built in which the pixels emit while the substrate remains see through, a configuration used in heads up displays and display cabinets. Since the three statements form a single chain of consequence, a candidate who grasps the emissive against transmissive distinction accepts all three, and the item is therefore decided by one concept rather than by three facts.
• Option (d) is a trap for over caution, inviting a candidate who doubts statement 2 as futuristic to reject the entire set.

• Option (c) is correct. Somatic cell nuclear transfer is the procedure in which the nucleus of a differentiated somatic cell of a donor animal is transferred into an oocyte from which the nucleus has been removed. The reconstructed cell is stimulated to divide and the resulting embryo is implanted in a surrogate, yielding an animal genetically identical to the nuclear donor. This is the technique by which Dolly the sheep was produced in 1996, and it is the standard method of reproductive cloning in mammals. Its scientific significance lies in demonstrating that differentiation does not entail irreversible loss of genetic information, since the oocyte cytoplasm can reprogramme an adult nucleus to totipotency.
• Option (a) is wrong because biolarvicides are microbial preparations, chiefly Bacillus thuringiensis israelensis and Bacillus sphaericus, produced by fermentation and unconnected with nuclear transfer.
• Option (b) is wrong because biodegradable plastics such as polyhydroxyalkanoates are made by microbial fermentation or from plant derived monomers.
• Option (d) is wrong and is the most plausible distractor, since disease free stock is produced by meristem tip culture in plants and by specific pathogen free husbandry in animals; nuclear transfer transmits the donor's genome entire, so it reproduces whatever genetic disease the donor carried rather than eliminating it. Governing principle: nuclear transfer copies a genome, and no copying technique can by itself remove disease.

• Option (b) is correct. eLISA, since adopted by the European Space Agency as LISA, is a space based gravitational wave observatory consisting of three spacecraft in a triangular formation trailing the Earth in solar orbit, separated by millions of kilometres, with laser links measuring changes in their separation to a precision of picometres. A passing gravitational wave alternately stretches and compresses spacetime along perpendicular directions, and the interferometer registers that strain as a change in optical path length. The purpose of going to space is bandwidth: ground based interferometers such as LIGO and Virgo have arm lengths of a few kilometres and are limited by seismic noise to frequencies above about ten hertz, which restricts them to stellar mass compact binaries in their final moments, whereas arms of millions of kilometres open the millihertz band, in which supermassive black hole mergers, extreme mass ratio inspirals and galactic compact binaries radiate.
• Option (a) is wrong: neutrino detection uses entirely different instruments, large volumes of water, ice or liquid scintillator observed by photomultipliers, as at Super-Kamiokande and IceCube, since neutrinos are detected through weak interactions and not through spacetime strain.
• Option (c) is wrong: interferometry has no application to missile defence assessment.
• Option (d) is wrong: solar flare effects on communications are studied by solar observatories and space weather monitors. Elimination route: the words 'Laser Interferometer' identify the instrument as a measurer of minute changes in path length, and of the four options only one describes a phenomenon that manifests as such a change.

• Statement 1 is correct. An open Application Programming Interface is a published contract, in this case an HTTPS and XML based one, that any application can call provided it conforms to the specification and is routed through an authorised Authentication User Agency. Because the interface is defined at the level of the network protocol rather than of a particular operating system or handset, it can be embedded in a point of sale terminal, a micro ATM, a mobile handset, a tablet or a kiosk, which is precisely what open means here.
• Statement 2 is correct. The Aadhaar authentication specification supports fingerprint, iris and one time password modalities, and iris authentication was available through registered iris devices well before this paper, having been introduced partly because iris performs better than fingerprint for manual labourers and the elderly whose ridge patterns are worn. Both statements being correct, the answer is (c). Governing principle: an open API is a contract, not a product, so the natural implication of openness is device and vendor independence, and the modalities supported are a separate question of specification, not of openness.

Hence (c).

• Option (d) is correct. Geographical indications are one of the seven categories of intellectual property covered by the Agreement on Trade Related Aspects of Intellectual Property Rights, which is Annexure 1C to the Marrakesh Agreement establishing the World Trade Organization. Articles 22 to 24 of TRIPS require members to provide legal means for interested parties to prevent misleading use of a geographical indication and to prevent unfair competition, with additional protection for wines and spirits. India, having had no sui generis law on the subject, enacted the 1999 Act and brought it into force in 2003 to discharge that obligation, the Darjeeling tea case having demonstrated how exposed Indian producers were without one.
• Option (a) is wrong because the International Labour Organization sets labour standards through conventions and recommendations and has no intellectual property mandate.
• Option (b) is wrong because the International Monetary Fund deals with exchange rates, balance of payments financing and macroeconomic surveillance.
• Option (c) is wrong and is the most instructive distractor, since the United Nations Conference on Trade and Development does work extensively on trade and development and on technology transfer, but it is a deliberative and research body that produces analysis and consensus texts, not binding obligations that require domestic legislation. Governing principle: only the World Trade Organization among the four generates treaty obligations enforceable through dispute settlement, and after 1995 nearly every Indian intellectual property statute or amendment traces to TRIPS.

Hence (d).

• Option (a) is the answer the key takes and it is correct in substance. The entire logic of India's post 2005 nuclear arrangements is a separation of the civilian from the strategic programme: designated civilian facilities are offered for safeguards while the military programme stays outside, and it is this bifurcation that made international nuclear commerce possible for a State outside the Non Proliferation Treaty.
• Option (b) is wrong precisely because it inverts that bargain; no instrument brings India's military nuclear installations under IAEA inspection, and had any done so the arrangement would have been politically impossible.
• Option (c) is wrong because uranium purchase rests on the clean waiver granted by the Nuclear Suppliers Group in September 2008 and on the bilateral agreements concluded afterwards with the United States, France, Russia, Kazakhstan, Canada and Australia; safeguards are a precondition for those transactions rather than the source of the entitlement, and the Group is in any event a set of guidelines rather than a seller.
• Option (d) is wrong for the same reason as statement 2 of question 7 in this paper: no safeguards instrument confers membership of the Nuclear Suppliers Group, which is decided by consensus among its participating governments and has repeatedly been withheld from India.

Hence (a).

• Option (c) is correct. Terminal High Altitude Area Defense is an American ballistic missile defence system, developed by Lockheed Martin and operated by the United States Army, designed to intercept short, medium and intermediate range ballistic missiles in their terminal phase at high altitude. It uses a hit to kill kinetic interceptor with no explosive warhead, destroying the target by the energy of impact, and is cued by the AN slash TPY 2 X band radar. Its deployment in the Republic of Korea from 2017 provoked sustained Chinese objection, ostensibly to the reach of the radar rather than to the interceptor.
• Option (a) is wrong: Israel's systems are Iron Dome for rockets and short range projectiles, David's Sling for medium range, and Arrow for longer range ballistic threats, and the radar in the Israeli architecture is the Green Pine rather than anything called THAAD.
• Option (b) is wrong: India's indigenous effort is the Ballistic Missile Defence programme of the Defence Research and Development Organisation, with the Prithvi Air Defence and Prithvi Defence Vehicle for exo atmospheric and the Advanced Air Defence for endo atmospheric interception.
• Option (d) is wrong: Japan and the Republic of Korea have no such joint programme, and Japan's own layered defence rests on Aegis equipped destroyers with SM 3 interceptors and on land based Patriot PAC 3. Note that the name states the function, terminal phase, high altitude, area rather than point defence, which is enough to identify it as an interceptor system rather than a radar and to eliminate option (a).

Hence (c).

All three are correct, and the reason is the same in each case, which is the point the question is really testing. A GPS receiver solves for four unknowns, three of position and one of time, so the system is as much a distributed atomic clock as a positioning service, and its precise timing signal is used far more widely than its coordinates.

• Statement 1 is correct: cellular base stations must be synchronised to a common time reference for handover between cells and for the timing structure of the air interface, and GPS disciplined oscillators are the usual source.
• Statement 2 is correct: banking and financial networks use GPS derived time to timestamp transactions, to sequence entries across distributed systems and to meet audit and regulatory requirements on clock accuracy, and this is the statement candidates most often reject because they think only of navigation.
• Statement 3 is correct: the phasor measurement units on which wide area monitoring of a power grid depends compare voltage and current phase angles at points hundreds of kilometres apart, and comparing phase across such distances is meaningless unless every unit is stamping its readings against the same clock to within microseconds. Since no statement can be rejected, only option (d) survives. Governing principle to carry: whenever GPS appears in a question outside navigation, ask whether the application needs a common time reference, and if it does the answer is almost always yes.

Hence (d).

• Option (c) is correct. All three terms belong to the same episode. EternalBlue is an exploit of a flaw in Microsoft's Server Message Block version 1 protocol, developed by the United States National Security Agency and released publicly by the Shadow Brokers group in April 2017. WannaCry, which spread worldwide in May 2017 and crippled parts of the British National Health Service among many others, was ransomware that used EternalBlue to propagate from machine to machine without user action, which is what made it a worm rather than an ordinary ransomware campaign. Petya, and more precisely the NotPetya variant of June 2017, used the same exploit but destroyed data irrecoverably while presenting itself as ransomware.
• Option (b) is the strongest distractor and is worth addressing carefully, because ransomware demands payment in Bitcoin and the two subjects are therefore linked in news coverage. The link is incidental: cryptocurrency is the payment channel, not the subject, and none of the three terms names a currency, a protocol or an exchange.
• Options (a) and (d) fail on domain, exoplanets and small satellites being unrelated to any of the three names. Governing principle for terms in news questions of this shape: find the single event that accounts for all the terms together rather than assessing each in isolation, since the examiner groups them precisely because they share one origin.

Hence (c).

• Statement 1 is correct and matches the published constellation design. IRNSS, operationally named NavIC, comprises seven satellites, three placed in geostationary orbit over the equator and four in inclined geosynchronous orbits that trace a figure of eight ground track, two of them crossing the equator at about 55 degrees east and two at about 111.75 degrees east. The inclined satellites exist to give good elevation angles over the whole service area, which a purely equatorial arrangement could not provide at northern latitudes.
• Statement 2 is incorrect on both the number and the unit, and the unit error alone should catch a careful reader. The service area extends about 1500 kilometres beyond India's borders, not 5500, and a coverage footprint beyond a border is a distance rather than an area, so the expression square kilometres beyond its borders is meaningless as written.
• Statement 3 is incorrect and contradicts the name of the system. IRNSS is by design a regional constellation; global coverage would require a far larger constellation in medium Earth orbit of the kind operated by GPS, GLONASS, Galileo and BeiDou, and India has announced no such system with a 2019 horizon. Elimination route: statement 3 can be rejected on the word Regional in the system's own title, which removes options (c) and (d); statement 2 then falls on the unit, leaving (a).

Hence (a).

• Statement 3 is the central content of the theory and is correct. General relativity replaces gravity as a force with the geometry of spacetime: the Einstein field equations relate the curvature of spacetime to the distribution of energy and momentum, so matter tells spacetime how to curve and curved spacetime tells matter how to move.
• Statement 1 is correct and is a direct consequence of statement 3. Since light follows null geodesics of the curved geometry, its path bends near a massive body, and it also loses frequency climbing out of a potential well. The deflection of starlight by the Sun measured at the 1919 eclipse was the observation that made the theory famous, and gravitational lensing is now a working tool of astronomy. Note that the Newtonian corpuscular calculation also predicts a deflection but only half the relativistic value, so the effect discriminates between the two theories rather than merely confirming that light responds to gravity.
• Statement 2 is the contested one and the key accepts it. The justification is that the field equations admit no stable static solution: Friedmann in 1922 and Lemaitre in 1927 showed that the generic cosmological solutions of general relativity are dynamic, either expanding or contracting, and Einstein had introduced the cosmological constant in 1917 precisely to force a static universe, later regarding that step as a mistake once Hubble's observations established recession. On that reading a non static universe is indeed a prediction of the theory and option (d) follows.

Hence (d).

• Statement 1 is incorrect and this is where most candidates go wrong, because the phrase genes of a soil bacterium is correct while the function attributed to them is not. DMH 11 carries the barnase, barstar and bar genes from Bacillus amyloliquefaciens, a soil bacterium, but these do not confer pest resistance. Barnase is a ribonuclease expressed in the tapetum that destroys pollen development and so induces male sterility; barstar is its specific inhibitor, restoring fertility in the hybrid; bar confers tolerance to the herbicide glufosinate and serves as the selectable marker. The pest resistance idea is imported from Bt cotton and brinjal, where the gene is from Bacillus thuringiensis and does confer insect resistance, and the examiner is testing whether the candidate can keep the two bacteria and the two purposes apart.
• Statement 2 is correct and describes exactly what the barnase and barstar system is for. Mustard is a self pollinating crop, which makes controlled crossing laborious and hybrid seed production commercially impractical; engineered male sterility with a fertility restorer supplies the tool that allows hybridisation and the capture of hybrid vigour.
• Statement 3 is incorrect. DMH 11 was developed by the Centre for Genetic Manipulation of Crop Plants at the University of Delhi South Campus under Deepak Pental, not by the Indian Agricultural Research Institute with Punjab Agricultural University. Elimination route: rejecting statement 3 removes options (a), (c) and (d) together and settles the question on one fact.

Hence (b).

• Pair 3 is incorrectly matched and it settles the question on its own. CRISPR Cas9 is a genome editing tool, adapted from a bacterial adaptive immune system in which short repeats store fragments of past viral invaders and the Cas9 nuclease, guided by a matching RNA, cuts double stranded DNA at a chosen sequence. It belongs to molecular biology and has nothing to do with particle physics. Since pair 3 appears in options (a), (c) and (d), rejecting it eliminates all three at once and leaves (b), which is why a candidate who knows only this one fact can answer with confidence.
• Pair 1 is also incorrectly matched, and the two errors are a straight swap. Belle II is a particle physics detector at the SuperKEKB electron positron collider at KEK in Japan, built to study rare decays of B mesons and charge parity violation, and thereby to look for physics beyond the Standard Model.
• Pair 2 is correctly matched. Blockchain is the distributed append only ledger, secured by cryptographic hashing and a consensus mechanism, on which Bitcoin and other cryptocurrencies are built, though the technology has applications well beyond currency, in land records, supply chain provenance and settlement systems.

Hence (b).

• Option (b) is correct. The scenario describes ordinary physical objects, a water heater, a mirror, a tank, a refrigerator, lighting and a car, each fitted with sensors and network connectivity so that they can gather data about their own state and about their environment, exchange it and act on it without human intervention. That is precisely the Internet of Things: the extension of network connectivity from computers and phones to everyday devices, together with the machine to machine communication and automated decision making that follows from it.
• Option (a) is wrong: the Border Gateway Protocol is the routing protocol that exchanges reachability information between autonomous systems and holds the backbone of the internet together; it is infrastructure invisible to any end device in this scenario.
• Option (c) is wrong for a subtler reason worth pressing, because every device described does use the Internet Protocol. But the Internet Protocol is merely the addressing and packet delivery layer, common to all networked communication whatsoever, so naming it explains nothing distinctive about the scenario; the question asks which term best applies, and a term that applies equally to sending an email is not the best fit.
• Option (d) is wrong: a Virtual Private Network is an encrypted tunnel that extends a private network across a public one, a security and access mechanism unrelated to device autonomy. Governing principle: identify what is novel in the description, which is that inanimate objects are the actors, and only one of the four terms names that.

Hence (b).

• Statement 1 is incorrect. India has almost no capacity in the upstream stages of the photovoltaic value chain. That chain runs from polysilicon to ingots, then wafers, then cells, then modules, and Indian manufacturing is concentrated almost entirely at the module assembly end, with limited cell capacity and effectively no commercial polysilicon, ingot or wafer production. China dominates wafer manufacture with a share above ninety per cent, and it is precisely this dependence on imported cells and wafers that prompted the safeguard duty debate of 2018 and the later production linked incentive scheme for solar modules.
• Statement 2 is incorrect and turns on the distinction between discovering a price and determining a tariff. The Solar Energy Corporation of India is a central public sector undertaking under the Ministry of New and Renewable Energy that acts as an implementing agency and an intermediary offtaker; it conducts reverse auctions in which developers bid, and the winning bid establishes the price. Determination and adoption of tariffs is a regulatory function vested in the Central Electricity Regulatory Commission and the State Electricity Regulatory Commissions under the Electricity Act, 2003, which adopt a competitively discovered tariff or fix one where there has been no competitive bidding. Both statements failing, the answer is (d). Elimination route: statement 2 rewards the general principle that in the Indian power sector the entity that runs a procurement is not the entity that regulates a tariff, and statement 1 rewards awareness that India imports the great bulk of its solar hardware.

Hence (d).

The key takes all five and the answer is (d).

• Statement 1 is correct: food printers extrude chocolate, sugar paste and dough layer by layer, and printed confectionery is an established niche in patisserie.
• Statement 2 is correct: the bionic ear demonstrated at Princeton in 2013 was printed from a hydrogel seeded with chondrocytes together with a silver nanoparticle coil, and is the standard cited example of printing a functional organ integrated with electronics.
• Statement 3 is correct: the automotive industry was among the earliest adopters, first for rapid prototyping of body panels and tooling and later for production of jigs, fixtures, brackets and low volume components.
• Statement 4 is correct and is now routine: patient specific titanium cranial and maxillofacial implants and surgical guides are printed from the patient's own computed tomography data, which is precisely the case additive manufacturing serves best, since every implant is a batch of one.
• Statement 5 is the doubtful one, and it survives on a permissive reading: printing is used to fabricate microfluidic devices, photonic and waveguide structures, heat sinks and interconnects, and printed electronics is a working field, so hardware used in data processing can be additively manufactured even though the printing of data processing itself is meaningless. Since no statement is rejected, only option (d) is available.

Hence (d).

• Statement 1 is correct and states the division of labour between the two vehicles accurately. The Polar Satellite Launch Vehicle is optimised for polar sun synchronous orbits at a few hundred kilometres, which is where remote sensing and Earth resources satellites belong, because a sun synchronous orbit crosses a given latitude at the same local solar time on every pass and so gives consistent illumination for comparing images across dates. The Geosynchronous Satellite Launch Vehicle, with its cryogenic upper stage, is built to place heavier payloads into geosynchronous transfer orbit, which is where communication satellites belong.
• Statement 2 is incorrect and follows directly from the first. Only a satellite in geostationary orbit, that is circular, equatorial and at about 35,786 kilometres where the orbital period matches the Earth's rotation, appears fixed in the sky. PSLV payloads are in low polar orbits with periods of roughly one hundred minutes, so they cross the sky rapidly and are visible from a given place only in short passes.
• Statement 3 is incorrect on the number of stages and on their arrangement. GSLV Mk III, now LVM3, is a three stage vehicle: two S200 solid strap on boosters, an L110 liquid core stage burning unsymmetrical dimethylhydrazine with nitrogen tetroxide, and the C25 cryogenic upper stage burning liquid hydrogen with liquid oxygen. There is no fourth stage. Elimination route: statement 2 is the cleanest reject, since the whole point of the geostationary orbit is that it is the only one giving a fixed apparent position, and rejecting it removes options (b) and (c); statement 1 is then secure and (a) follows.

Hence (a).

All four disperse plant pathogens and the answer is (d).

• Item 1 is correct: birds carry spores, bacteria and viruses on feet, feathers and beak from plant to plant, transmit some pathogens through droppings, and create the wounds through which infection enters when they peck at fruit; they also carry infected insect vectors.
• Item 2 is correct: wind blown dust and soil particles carry fungal spores, bacteria, nematode cysts and resting structures over long distances, and abrasion by blown particles also injures leaf surfaces and opens entry points, which is why dust storms precede outbreaks in semi arid cropping systems.
• Item 3 is correct and operates by two distinct mechanisms: rain splash physically ejects spores and bacterial cells from infected tissue and soil onto healthy foliage above, which is the principal short range dispersal route for many bacterial blights and for anthracnose, and prolonged leaf wetness supplies the free water that spores need to germinate and penetrate.
• Item 4 is correct and is the most familiar route, wind carrying rust urediniospores across hundreds of kilometres, which is how wheat rusts move from one region to another between seasons. Since no item can be rejected, only option (d) survives and no elimination is needed. Governing principle: a plant pathogen is immobile and must be carried, so almost any agent that moves material between plants, whether animal, particle, water or air, is a potential means of dissemination.

Hence (d).

• Statement 1 is correct. Chlorophyll absorbs strongly in the red and reflects strongly in the near infrared, and this contrast is exactly what vegetation indices such as NDVI exploit; chlorophyll concentration in both terrestrial vegetation and ocean phytoplankton is a routine remote sensing product.
• Statement 3 is correct. Land surface temperature is retrieved from the thermal infrared bands carried by sensors such as Landsat TIRS and MODIS, and urban heat island mapping rests on it.
• Statement 2 is the statement that gives the item its difficulty, and it is also correct. Methane emissions from rice paddies are estimated by remote sensing, though indirectly, by mapping flooded paddy extent and cropping calendar from optical and synthetic aperture radar data and combining that with emission factors in a model, while atmospheric methane column concentrations are separately retrieved by instruments such as SCIAMACHY, GOSAT and later TROPOMI. Since all three hold, the official answer (d) follows. The governing principle is that remote sensing measures reflected and emitted electromagnetic radiation across the spectrum, and once a candidate accepts that thermal and infrared bands are available alongside the visible, the only reason to doubt statement 2 is an unstated assumption that estimation must mean direct measurement.

• Statement 1 is incorrect. Section 3(j) of the Patents Act, 1970 excludes from patentability plants and animals in whole or any part thereof other than micro organisms, including seeds, varieties and species, and essentially biological processes for the production or propagation of plants and animals. A biological process to create a seed therefore falls squarely within the exclusion.
• Statement 2 is incorrect as of the date of the paper. The Intellectual Property Appellate Board was constituted in 2003 under the Trade Marks Act, 1999 and heard appeals in trade mark, patent, geographical indication and later copyright matters, and it was functioning in 2019.
• Statement 3 is correct, and it is the corollary of statement 1. Plant varieties are not patentable in India; they are protected instead by a sui generis regime under the Protection of Plant Varieties and Farmers' Rights Act, 2001, which India enacted to meet its TRIPS Article 27.3(b) obligation while preserving farmers' rights to save, use, sow and exchange seed. Since only statement 3 holds, the official answer (c) follows. The governing principle is the sui generis route, which explains both why plant varieties are excluded from patenting and where their protection actually lives.

• Statement 1 is incorrect. LTE is marketed as 4G, not 3G, and VoLTE is marketed as advanced 4G or as HD voice. The 3G designation belongs to the earlier UMTS and CDMA2000 family, and the generational label is exactly what the statement gets wrong.
• Statement 2 is incorrect on its second half. LTE in its native form is indeed an all internet protocol, packet switched, data only bearer, which is why early LTE networks had to fall back to a legacy circuit switched network to carry a voice call, the technique known as circuit switched fallback. VoLTE is the solution to that problem: it carries voice as packets over the same LTE data bearer using the IP Multimedia Subsystem, with quality of service priority assigned to the voice packets. VoLTE is therefore voice over a data network, not a voice only technology, and a VoLTE capable network continues to carry data simultaneously, which is precisely its advantage over circuit switched fallback. Since both statements fail, the official answer (d) follows. The governing insight is that VoLTE is not a different generation or a different network from LTE at all; it is a service delivered over LTE, so any statement that opposes the two as separate technologies is suspect on its face.

• Statements 1 and 2 are a straight interchange of the two definitions, and statements 3 and 4 state them correctly, which is the entire architecture of the question.
• Statement 1 is incorrect because the creation of a simulated environment that shuts out the physical world is virtual reality, not augmented reality.
• Statement 2 is incorrect for the mirror reason, because the projection of computer generated images onto real objects and surroundings is augmented reality, not virtual reality.
• Statement 3 is correct: augmented reality keeps the user in the real world and overlays information on it, typically through the camera of a phone, tablet or headset, Pokemon Go and camera based navigation and translation overlays being the familiar examples.
• Statement 4 is correct: virtual reality closes off the real world through a head mounted display and transposes the user into a wholly generated environment, aiming at complete immersion. Since statements 3 and 4 hold, the official answer (b) follows. The governing test is the single word augmented, which means added to something already there, so augmented reality must retain the real world and virtual reality must replace it. Holding the meaning of the word alone is sufficient, and no candidate needs to have used either technology.

Denisovans are an extinct group of archaic humans, a sister population to the Neanderthals, first identified in 2010 not from skeletal morphology but from DNA extracted from a finger bone and teeth found in Denisova Cave in the Altai mountains of Siberia, so (b) is correct. They are significant because the species was defined by genomics before it was described from anatomy, and because their genetic legacy survives in living people: Melanesians, Papuans and Aboriginal Australians carry several per cent of Denisovan ancestry, and the high altitude adaptation allele EPAS1 in Tibetans is of Denisovan origin, evidence of interbreeding with anatomically modern humans.

• Option (a) is wrong; the group is hominin and belongs to the late Pleistocene, tens of thousands rather than tens of millions of years ago.
• Option (c) is wrong, and is the deliberate trap for an Indian candidate, since Denisova Cave is in Siberia and the North East Indian cave associations are with the Meghalaya limestone systems, one of which gives its name to the Meghalayan Age.
• Option (d) is wrong for the same reason; the geological stage named from India is the Meghalayan, ratified in 2018, not anything Denisovan. The name itself is the guide, being a place name in the Altai, and the discipline is to resist the pull of the plausible Indian option.

• Option (b) is correct as a statement of fact. Artificial functional DNA has been synthesised in laboratories, from the chemical synthesis of a complete bacterial genome in the Mycoplasma work of the Venter group to the construction of synthetic gene circuits and of expanded genetic alphabets.
• Option (c) is correct, and describes something done routinely. The polymerase chain reaction replicates a defined stretch of DNA in a tube, outside any living cell, using a thermostable polymerase, primers and thermal cycling; cell free replication is ordinary laboratory practice.
• Option (d) is correct. Plant and animal cells are cultured and divided in petri dishes as a matter of routine, plant tissue culture and micropropagation on one side and mammalian cell culture on the other.
• Option (a) is the statement the key marks as not correct, and this is where the item is weak. Chromosomes assembled from DNA of more than one species are not beyond reach: yeast artificial chromosomes routinely carry large inserts of foreign DNA and function through mitosis, the Sc2.0 project has synthesised and substituted functional yeast chromosomes, and in 2018 two groups fused the sixteen yeast chromosomes into one and two respectively while retaining viability. A candidate can reach (a) only by elimination, having satisfied himself that the other three are unarguable.

• Statement 3 is correct and states what a digital signature is. The signer's private key is applied to a hash of the document, producing a value that anyone holding the corresponding public key can verify; verification establishes both that the signer's key was used and that the content has not been altered since signing, since any change to the document changes its hash and breaks the verification. Authentication and integrity together are the definition.
• Statement 1 is treated by the key as incorrect because it describes a different object. An electronic record that identifies the issuing certifying authority is a Digital Signature Certificate, the credential that binds a public key to an identity and carries the issuing authority's own signature. The certificate identifies the certifying authority; the signature does not.
• Statement 2 is the statement the key rejects with least justification. Since only statement 3 survives, the official answer (c) follows. The distinction the question is testing is between the signature, which is an operation performed on a document, and the certificate, which is a credential vouching for a key, and holding that distinction is the only reliable route through the item.

The significance of observing a black hole merger at cosmological distance is that the merger is detected through the gravitational waves it emits, so (b) is correct. General relativity predicts that accelerating masses radiate ripples in spacetime; the final inspiral and coalescence of two black holes is among the most powerful sources, and the passing wave produces a fractional change in length far smaller than a proton diameter, which the kilometre scale laser interferometers of LIGO and Virgo detect as a shift in the interference pattern between their perpendicular arms. The first detection, of a merger about 1.3 billion light years away, was announced in February 2016 and the Nobel Prize followed in 2017.

• Option (a) is wrong because the Higgs boson is a particle of the Standard Model detected at the Large Hadron Collider in 2012 through proton collisions, an entirely different physics and a laboratory rather than an astronomical observation.
• Option (c) is wrong because wormholes remain a theoretical solution of the field equations with no observational support whatever, and nothing in a merger observation bears on traversability.
• Option (d) is wrong because the singularity at the centre of a black hole is precisely what is not observed; the waveform carries information about the masses, spins and orbital dynamics outside the horizon, and the classical singularity remains outside the reach of both observation and current theory.

Cas9 is a CRISPR associated endonuclease, an enzyme that cuts double stranded DNA, so (a) is correct. In the CRISPR Cas9 system a guide RNA carrying a sequence complementary to the intended target directs the Cas9 protein to that site in the genome, where it cleaves both strands adjacent to a short protospacer adjacent motif. The cell's own repair machinery then either rejoins the ends imprecisely, disrupting the gene, or, if a template is supplied, repairs the break by homologous recombination, allowing a sequence to be inserted or corrected. The description as molecular scissors captures this cutting function, and the guide RNA is what makes the cutting targeted.

• Option (b) is wrong as stated, although it is the most interesting distractor, since Cas enzymes have since been adapted into diagnostic platforms; Cas9 itself is a nuclease, not a biosensor.
• Option (c) is wrong because Cas9 is a protein of bacterial adaptive immunity, not a plant pest resistance gene, that role belonging to Bt cry genes.
• Option (d) is wrong because Cas9 is not a herbicide; herbicide tolerance in genetically modified crops works by an altered target enzyme such as EPSPS in glyphosate tolerant lines. The governing point is that CRISPR supplies the address and Cas9 supplies the blade.

• Option (b) is the statement that is not correct, and it inverts the true position exactly. A safe and effective recombinant vaccine against hepatitis B has existed since the 1980s and is part of India's Universal Immunisation Programme, given at birth and in the pentavalent schedule. Hepatitis C has no vaccine, the virus's genetic diversity and rapid mutation having defeated development so far, though it has become curable with direct acting antivirals achieving cure rates above ninety five per cent. The statement therefore reverses which of the two has a vaccine.
• Option (a) is correct: hepatitis B is transmitted by blood, by sexual contact and from mother to child, the same routes as HIV, and it is considerably more infectious by those routes.
• Option (c) is correct: the global burden of chronic hepatitis B and C together is of the order of three hundred million people against roughly forty million living with HIV, several times more.
• Option (d) is correct and is the reason the disease is called silent; chronic infection may run for decades without symptoms and present only at the stage of cirrhosis or hepatocellular carcinoma, which is why screening rather than symptom based diagnosis is the public health strategy. The organising fact to carry is the asymmetry: hepatitis B has a vaccine but no cure, hepatitis C has a cure but no vaccine.

Pronuclear transfer is one of the two principal mitochondrial replacement techniques. Both the mother's egg and a donor egg are fertilised, the two pronuclei are removed from the mother's zygote and transferred into the enucleated donor zygote, which retains healthy donor mitochondria. The child inherits nuclear DNA from both parents and mitochondrial DNA from the donor, so maternally transmitted mitochondrial disease is avoided. Hence (d).

• Option (a) is wrong because in vitro fertilisation of an egg by sperm is ordinary IVF or, where a single sperm is injected, intracytoplasmic sperm injection.
• Option (b) is wrong because that describes germline gene therapy directed at spermatogonial cells, an entirely separate line of work.
• Option (c) is wrong because deriving embryos or embryo like structures from stem cells is the field of synthetic embryology, unrelated to pronuclear manipulation.

• Statement 1 is correct, since reinforcement learning applied to cooling and process control has demonstrably cut industrial and data centre energy use.
• Statement 3 is correct, since image classification models are in clinical use for diabetic retinopathy, tuberculosis screening and histopathology.
• Statement 4 is correct, since neural text to speech is mature and deployed.
• Statement 5 is clearly incorrect, since wireless power transfer is a problem of electromagnetic induction and resonance in physics and hardware, and no software technique can accomplish it.
• Statement 2 is treated as incorrect by the official key, on the view that machine generated stories and songs then lacked genuine meaning. The answer as keyed is 1, 3 and 4, giving (b).
• Options (a), (c) and (d) all admit the wireless power error.

• Statement 1 is correct, since roughly 380 to 780 nanometres is the visible band and VLC modulates light emitting diodes within it.
• Statement 2 is incorrect and is the discriminating statement. VLC is inherently short range and requires line of sight, since visible light neither penetrates walls nor travels far without collimation; long range optical wireless is free space optical communication, a distinct technology.
• Statement 3 is correct, since demonstrated VLC data rates run into gigabits per second against a few megabits per second for classic Bluetooth.
• Statement 4 is correct in the practical sense, since VLC does not interfere with radio frequency equipment, which is why it is attractive in aircraft cabins, operating theatres and other electromagnetically sensitive spaces. The answer is 1, 3 and 4, giving (c).

• Statement 1 is correct as a description of a public permissionless chain, which is a distributed append only ledger replicated across nodes, open to inspection and controlled by no single participant, with consensus rather than an administrator determining validity.
• Statement 2 is incorrect and is the obvious eliminator. Cryptocurrency was the first application, not the structure; the same ledger carries land records, supply chain provenance, digital certificates and smart contracts.
• Statement 3 is correct, since a permissionless chain requires no gatekeeper's approval to build upon, which is the precise sense in which the technology is called permissionless. The answer is 1 and 3, giving (d).
• Options (b) and (c) rest on the cryptocurrency only error, and (a) drops the permissionless character, which is one of the defining features.

• Statement 1 is correct, since functionalised nanotubes are established vehicles for drug and antigen delivery, the high surface area and ability to cross membranes being the attraction.
• Statement 3 is correct, since their electrical conductivity changes on binding of a target molecule, which is the basis of nanotube field effect biosensors.
• Statement 4 is accepted as correct by the key on the strength of work showing enzymatic degradation of carboxylated nanotubes by peroxidases, including myeloperoxidase released by neutrophils.
• Statement 2 is treated as incorrect by the key. The keyed answer is therefore 1, 3 and 4, giving (c), with (a) and (d) rejected for including statement 2 and (b) rejected for dropping statement 1.

The description matches a space based gravitational wave observatory, in which laser interferometry between free falling test masses measures the minute changes in separation produced by a passing wave. Only the Evolved LISA concept involves three spacecraft in an equilateral formation with arms of order a million kilometres, so (d) is correct.

• Option (c) is the intended trap and is wrong because LISA Pathfinder, launched in 2015, was a single spacecraft carrying two test masses a few tens of centimetres apart, a technology demonstrator for drag free control rather than an interferometer between craft.
• Option (a) is wrong because Voyager 2 is a single outer planet flyby probe now in interstellar space.
• Option (b) is wrong because New Horizons is a single spacecraft that flew past Pluto in 2015 and the Kuiper belt object Arrokoth in 2019.

• Statement 1 is correct, since germline editing of gametes and of the gamete producing cells is technically achievable, whatever the ethical and regulatory bar on its use.
• Statement 2 is correct, since editing at the zygote or early embryo stage is precisely what was done in the 2018 episode in China, and the resulting change is heritable because it is present in every cell.
• Statement 3 is correct, since human induced pluripotent stem cells have been injected into pig embryos to create interspecies chimeras, work directed at eventual organ generation, though the contribution of human cells has remained very low. All three stand, giving (d). Each of options (a), (b) and (c) rests on treating one demonstrated capability as impossible. The general principle to teach here is that the question asks what can be done, not what is permitted.

• Statement 1 is correct. Streptococcus pneumoniae causes not only pneumonia but also bacterial meningitis, septicaemia and otitis media, and the conjugate vaccine protects against the invasive forms as well.
• Statement 2 is correct and is the antimicrobial resistance argument for vaccination. Preventing infection removes the occasion for antibiotic use, and pneumococcus has developed resistance to penicillins and macrolides, so reducing case load directly reduces reliance on drugs that are losing effectiveness.
• Statement 3 is incorrect and is disposed of by the absolute phrasing alone. No vaccine is free of adverse events; injection site reactions, fever and rare hypersensitivity occur with conjugate vaccines as with others. The answer is 1 and 2, giving (b).
• Options (c) and (d) fail on the no side effects claim and (a) drops the resistance argument.

• Statement 1 is correct. The cellulose wall external to the plasma membrane is the classic plant feature, absent in animal cells, which have only the membrane and an extracellular matrix.
• Statement 2 is incorrect and is decisive. Every living cell, plant, animal, fungal or bacterial, possesses a plasma membrane, since without it there is no cell; the plant cell has a wall in addition to the membrane, not instead of it.
• Statement 3 is correct. A mature plant cell is dominated by a single large central vacuole that maintains turgor and stores solutes, whereas animal cells contain small and transient vacuoles and vesicles. The answer is 1 and 3, giving (c).
• Options (a), (b) and (d) all admit the plasma membrane error, so recognising that single point settles the question.

Under the separation plan that followed the India United States civil nuclear agreement of 2008, India divided its reactors into a civilian list and a strategic list. Reactors that use imported uranium, or that were built with foreign assistance, are placed on the civilian list and accept International Atomic Energy Agency safeguards, which verify that the fuel is not diverted to weapons use. Reactors running on domestically mined uranium remain outside safeguards, preserving freedom of action for the strategic programme. Hence (b).

• Option (a) is wrong because no Indian power reactor runs on thorium as primary fuel; thorium enters only in the third stage of the programme, and safeguards attach to fuel origin rather than fuel type.
• Option (c) is wrong because no reactor in India is operated by a foreign enterprise.
• Option (d) is wrong because there is no private ownership of reactors, operation resting with the Nuclear Power Corporation and Bhavini.

The reasoning here is first principles rather than recall. Solar photovoltaic panels supply electricity, and once electricity is available the pump does not know or care where it came from. What the panel constrains is the power available and its variation through the day, not the type of pump.

• Statement 1 is therefore incorrect, and solar submersible pumps are in fact the commoner configuration in India because groundwater tables lie below the suction limit of a surface pump.
• Statement 2 is incorrect for the same reason. Centrifugal pumps are usual because they suit continuously variable speed drives, but positive displacement pumps including piston and helical rotor types are used with solar arrays, and they are preferred at low flow and high head. Neither statement stands, giving (d).
• Options (a), (b) and (c) all treat the energy source as though it dictated the mechanical design.

• Statement 1 is correct. In the bud chip method only the bud along with a small portion of adjoining cane is scooped out and raised in a nursery, so the remaining cane is available for milling, and seed material requirement falls sharply against conventional planting of two or three budded setts.
• Statement 4 is correct. Micropropagation from meristem tissue is used to multiply disease free planting material rapidly and is standard in seed cane programmes.
• Statements 2 and 3 are both incorrect and both invert the underlying agronomy. A sett with several buds carries more stored food and moisture in the internodes, so it germinates at a higher percentage and survives adverse weather better than a single budded sett, which has a small reserve and desiccates or rots more readily. The answer is 1 and 4, giving (c). The single budded sett is chosen to economise on seed, not because it establishes better, and options (a), (b) and (d) all confuse those two things.

Both statements are correct.

• Statement 1 holds by definition: a recombinant vector vaccine is constructed by inserting the gene encoding an antigen of the target pathogen into the genome of a carrier organism, which is genetic engineering in the strict sense.
• Statement 2 holds because both bacterial and viral vectors are used. Attenuated adenoviruses are the best known viral vectors, used in the Oxford AstraZeneca chimpanzee adenovirus platform, in Sputnik V and in the Johnson and Johnson vaccine, while attenuated bacteria such as Salmonella and BCG have been employed as bacterial vectors, particularly for mucosal delivery. Hence (c). The conceptual point worth drawing out for students is that the vector delivers the genetic instruction and the host's own cells manufacture the antigen, which is what distinguishes this platform from subunit and inactivated vaccines.

• Statement 2 is correct and is the foundational fact: mitochondria are inherited exclusively through the oocyte cytoplasm, because the few paternal mitochondria that enter at fertilisation are selectively degraded, so mitochondrial disease follows a strictly maternal line of transmission.
• Statement 1 is correct and follows from it: mitochondrial replacement therapy transfers the nuclear genome from an affected woman's egg or zygote into a donor egg or zygote whose own nucleus has been removed but whose mitochondria are healthy. This can be done before fertilisation by maternal spindle transfer, or after fertilisation by pronuclear transfer, so the phrase either before or after in vitro fertilization is accurate and is the precise point being tested. Hence (c). The technique is the origin of the loose journalistic phrase three parent baby, and the resulting child carries nuclear DNA from two parents and mitochondrial DNA from a third.

Bollgard is the Monsanto trade name for Bt cotton. Bollgard I carries a single gene, cry1Ac, from Bacillus thuringiensis, expressing a crystal protein toxic to lepidopteran bollworms. Bollgard II stacks two genes, cry1Ac and cry2Ab, which broadens the pest spectrum and, importantly, delays the evolution of resistance, since an insect must acquire resistance to both toxins simultaneously. Both are therefore transgenic crop technologies, making option (b) correct.

• Option (a) is wrong because clonal propagation is tissue culture, involving no gene transfer.
• Option (c) is wrong because plant growth substances are auxins, gibberellins and cytokinins.
• Option (d) is wrong because biofertilisers are microbial inoculants such as Rhizobium and Azotobacter. Hence (b). Bt cotton remains the only GM crop approved for commercial cultivation in India, which is a fact worth stating precisely whenever this topic arises.

The cooking temperature is the boiling point of water at the pressure maintained inside the vessel, and that pressure is set by the condition for the weight to lift. The steam must exert a force exceeding the weight of the regulator, so the gauge pressure at which venting begins is the weight divided by the area of the vent hole.

• Item 3 is therefore correct, since a heavier weight demands higher pressure.
• Item 1 is correct, since for a given weight a smaller hole area means a higher pressure is needed to produce the required lifting force, and the two together fix the operating pressure.
• Item 2 is incorrect and is the key exclusion: a hotter flame raises the rate of steam generation and so shortens the time to reach operating pressure, but it cannot raise the pressure beyond the point at which the weight lifts and vents the excess. The flame governs how fast, not how hot. Hence 1 and 3, giving (c). This is a clean application of the Clausius Clapeyron relation between pressure and boiling point, and is a good classroom example of a regulated equilibrium.

• Statement 1 is incorrect on both limbs, which is unusual and makes it easier once the biology is secure. Adenoviruses have double stranded DNA genomes, not single stranded. Retroviruses have single stranded RNA genomes, not double stranded DNA, and their defining feature is reverse transcriptase, which copies that RNA into DNA for integration into the host chromosome, the very reversal of the central dogma from which the group takes its name.
• Statement 2 is correct: adenoviruses are among the agents of the common cold, alongside rhinoviruses and coronaviruses, and AIDS is caused by HIV, a retrovirus of the lentivirus genus. Hence (b). A candidate who remembers only that retroviruses are RNA viruses can reject statement 1 outright and reach the answer.

The water molecule is bent with an angle of about 104.5 degrees, and because oxygen is far more electronegative than hydrogen the molecule carries a permanent dipole moment. That dipole allows water to surround ions, orienting its negative oxygen end towards cations and its positive hydrogen ends towards anions, which is hydration, and the energy released in doing so overcomes the lattice energy holding the solid together. This is why water is called the universal solvent, so option (a) is correct.

• Option (b) is irrelevant, since thermal conductivity has no bearing on solvation.
• Option (c) is a genuine property of water but explains its thermal buffering of climate and organisms, not its dissolving power.
• Option (d) merely restates the composition without supplying a mechanism, and many oxides are not solvents at all. Hence (a). The question rewards distinguishing a true statement from an explanatory one.

• Statement 1 is correct: a sodium lamp is a gas discharge tube radiating in all directions, so reflectors are needed to direct the output downward and much is wasted as glare and sky glow, whereas an LED is a semiconductor junction emitting into a hemisphere, which is why LED luminaires deliver more usable light per watt onto the road surface.
• Statement 3 is correct: the sodium D lines at about 589 nanometres make low pressure sodium light almost monochromatic yellow, under which colours cannot be distinguished, while LEDs provide broad spectrum white light with far better colour rendering, an appreciable safety advantage.
• Statement 2 is incorrect and is the decisive statement: LEDs substantially outlast sodium lamps, typically fifty thousand hours against fifteen to twenty four thousand, and this longevity together with efficiency is the entire economic case for the replacement programme. Hence 1 and 3, giving (c). Note that if statement 2 were true the national LED retrofit would make little sense, which is a useful plausibility check.

ACE2 is angiotensin converting enzyme 2, a membrane bound enzyme of the renin angiotensin system present on cells of the respiratory epithelium, intestine, heart and kidney. It became globally significant because the spike protein of SARS-CoV-2 binds ACE2 to gain entry into host cells, which explains both the tissue distribution of COVID-19 damage and the design of vaccines and therapeutics targeting that interaction.

• Option (d) is therefore correct.
• Option (a) is wrong because transgenic plant genes are designated cry, bar and similar.
• Option (b) is wrong because India's navigation system is NavIC, built on the IRNSS constellation.
• Option (c) is wrong because radio collars involve VHF and satellite telemetry, not enzyme nomenclature.

Hence (d).

A unit of measurement is useful only if it is invariant, and the light-year is defined as the distance light travels in vacuum in one Julian year. That definition is reliable precisely because the speed of light in vacuum is a universal constant, identical for every observer regardless of relative motion, which is the second postulate of special relativity and now fixes the metre itself by definition.

• Option (d) is therefore correct.
• Option (a) is false as a matter of fact, since stellar distances change continuously through proper motion and cosmological expansion, and it would in any case not justify the choice of unit.
• Option (b) is irrelevant to distance measurement and also untrue in general.
• Option (c) is both physically inaccurate, since light bends in a gravitational field as gravitational lensing demonstrates, and insufficient, because straightness of path says nothing about the constancy of the scale. Hence (d). The question is really asking what property makes a good standard, which is a point worth generalising to the SI base units.

• Statement 1 is correct. Monazite is a phosphate of the light rare earth elements, chiefly cerium, lanthanum, neodymium and praseodymium, and it is the principal rare earth bearing mineral worked in India.
• Statement 2 is correct. Monazite characteristically carries thorium in the lattice, typically of the order of eight to ten per cent as thorium dioxide, which is why India's beach sands underpin the thorium based third stage of the nuclear programme.
• Statement 3 is incorrect, and the word entire is the giveaway. Monazite occurs in economically significant concentration only in particular placer deposits, principally along the Kerala and Tamil Nadu coasts and in parts of Odisha and Andhra Pradesh, where wave and current sorting has concentrated the heavy minerals. Long stretches of the Indian coast carry no such deposits.
• Statement 4 is correct. Monazite is a prescribed substance under the Atomic Energy Act on account of its thorium content, and its processing and export are reserved to government entities, in practice Indian Rare Earths Limited, while private operators may handle the other beach sand minerals.
• Statements 1, 2 and 4 hold, giving (b).
• Options (a), (c) and (d) each admit the overstated distribution claim in statement 3.

All three statements describe the defining claims of Web 3.0 as the term is currently used.

• Statement 1 is correct because the central proposition of Web 3.0 is user ownership of data, with identity and records held in user controlled wallets or decentralised identifiers rather than in the databases of platform companies.
• Statement 2 is correct because blockchain based social networks, in which the social graph and the content are recorded on a distributed ledger rather than on a company's servers, are among the most cited applications of the model.
• Statement 3 is correct in the same sense, describing collective operation by users through distributed nodes and, in the fuller versions of the idea, through decentralised autonomous organisations that hold governance rights, as against a single corporation owning and operating the service. All three holding, (d) is correct, and options (a), (b) and (c) each drop one of the three characteristic claims.

Software as a Service is the cloud delivery model in which an application is hosted centrally by a provider and consumed by subscribers over a network, with the provider retaining responsibility for the infrastructure, the platform and the application itself.

• Statement 1 is correct. Within the limits the vendor exposes, subscribers routinely configure the user interface and define or modify data fields, which is how a single hosted instance serves many organisations with different requirements.
• Statement 2 is correct and follows directly from the delivery model: because the application and the data sit on the provider's infrastructure and are reached over the network, any authorised device including a mobile handset can access them.
• Statement 3 is correct. Web based mail services are the most familiar consumer instance of SaaS, since the user runs no software locally and the provider hosts the application and stores the data. All three holding, (d) is correct, and options (a), (b) and (c) each drop a true statement.

A fractional orbital bombardment system delivers a warhead by first placing it in a low orbit and then braking it out of that orbit over the target, instead of flying the high ballistic arc of a conventional intercontinental missile. The military attraction is that the trajectory is low and can approach from any direction, including over the South Pole, which defeats early warning radars oriented along expected ballistic corridors and compresses warning time.

• Option (c) captures this and is correct.
• Option (a) describes planetary defence against an asteroid, an entirely civilian application with no bombardment of a terrestrial target.
• Option (b) describes an orbiter and lander sequence of the kind used in interplanetary missions.
• Option (d) describes a comet rendezvous and lander, the profile flown by Rosetta and Philae.

Hence (c).

A qubit, or quantum bit, is the unit of information in quantum computing. Where a classical bit must be either zero or one, a qubit is a two level quantum system whose state is in general a superposition of the two basis states, and multiple qubits can be entangled so that the state of the register cannot be described as a mere list of individual qubit states. It is this superposition and entanglement that permit quantum algorithms to explore a computational space in a way classical hardware cannot.

• Option (b) is therefore correct.
• Option (a) is wrong because cloud services are a delivery model for classical computing resources and carry no such unit, notwithstanding that quantum processors are now offered over the cloud.
• Options (c) and (d) are wrong because visible light communication and wireless communication are transmission technologies whose vocabulary concerns modulation, bandwidth and spectrum, not quantum states.

A biofilm is a community of microorganisms adhering to a surface and embedded in a self produced matrix of extracellular polymeric substances, and the three statements describe its best documented properties.

• Statement 1 is correct: catheters, prosthetic joints, heart valves and other indwelling devices are classic substrates, and device associated biofilm infection is a major clinical problem precisely because the implant offers an abiotic surface shielded from host defences.
• Statement 2 is correct: biofilms form readily on food contact surfaces and processing equipment, which is why sanitation regimes in food plants target them specifically.
• Statement 3 is correct and is the property that matters most clinically. Cells within a biofilm tolerate antibiotic concentrations orders of magnitude above those that kill the same organisms in free floating culture, because the matrix impedes penetration, the interior cells are metabolically slow and so escape agents that act on growing cells, and persister subpopulations survive treatment. All three holding, (d) is correct; options (a), (b) and (c) each omit a well established property.

• Statement 1 is correct. Probiotic preparations draw on both bacteria, chiefly lactic acid bacteria of the genera Lactobacillus and Bifidobacterium, and yeasts, of which Saccharomyces boulardii is the standard example used against antibiotic associated diarrhoea.
• Statement 2 is incorrect, and it is the discriminating statement. Probiotic organisms are not foreign to the human gut; lactobacilli and bifidobacteria are ordinary residents of the healthy intestinal flora, and the rationale of probiotic administration is to restore or reinforce a population that already belongs there rather than to introduce an alien one.
• Statement 3 is correct. Lactic acid bacteria produce beta galactosidase, which hydrolyses lactose, so probiotic and fermented dairy products improve the tolerance of milk sugar in individuals with low intestinal lactase, which is the observed benefit in lactose maldigestion.
• Statements 1 and 3 hold and 2 fails, giving (c).
• Options (b) and (d) admit the false claim that these organisms do not occur naturally in the gut, and (a) drops the well supported statement 3.

• Statement 1 is incorrect. Covishield, manufactured by the Serum Institute of India under licence from Oxford and AstraZeneca, is a replication deficient chimpanzee adenovirus vector carrying the gene for the spike protein. It is not an mRNA vaccine; the mRNA platform in the COVID-19 context belongs to the Pfizer BioNTech and Moderna products, neither of which was made by the Serum Institute.
• Statement 2 is correct. Sputnik V is a viral vector vaccine and is distinctive in using two different adenovirus vectors, Ad26 for the first dose and Ad5 for the second, a heterologous prime boost designed to avoid the anti vector immunity that would blunt a repeat dose of the same vector.
• Statement 3 is correct. COVAXIN, developed by Bharat Biotech with the Indian Council of Medical Research and the National Institute of Virology, is a whole virion inactivated vaccine, in which the virus is killed and presented with an adjuvant.
• Statements 2 and 3 holding, (b) is correct, and options (a), (c) and (d) each accept the platform error in statement 1.

The effects of a severe geomagnetic storm follow from the coupling of solar energetic particles and the interplanetary magnetic field to the earth's magnetosphere and ionosphere.

• Item 1 holds because ionospheric disturbance corrupts the propagation delay of satellite navigation signals and degrades or denies a position fix.
• Item 3 holds because a rapidly varying geomagnetic field induces currents in long conductors, and these geomagnetically induced currents can saturate and damage grid transformers, as at Quebec in 1989.
• Item 4 holds because energetic particles precipitating along field lines excite atmospheric atoms, and in a severe storm the auroral oval expands far towards the equator.
• Item 6 holds because absorption of energy heats and expands the upper atmosphere, raising drag on low orbiting satellites and decaying their orbits.
• Item 7 holds because polar routes depend on high frequency radio, and enhanced ionisation absorbs those signals during a storm.
• Item 2 fails because tsunamis are generated by the sudden displacement of a water column through seismic or landslide events; there is no mechanism by which a magnetic disturbance moves the ocean floor.
• Item 5 fails likewise, since no plausible energy pathway ignites forests worldwide.
• Items 1, 3, 4, 6 and 7 therefore hold, giving (c), and options (a), (b) and (d) each admit the tsunami or forest fire claim, which offers a clean elimination route.

• Statement 1 is correct. Polyethylene terephthalate drawn into fibre is polyester, and polyester and cotton or polyester and wool blends are among the commonest textile constructions, the synthetic component contributing strength, crease resistance and dimensional stability to the natural fibre.
• Statement 2 is incorrect, and the word any is what defeats it. PET is standard for water and carbonated soft drinks, but it is not suitable for the whole range of alcoholic beverages; spirits of high alcohol content act as a solvent on the polymer over time, promoting migration of monomer and additives, and PET's permeability to oxygen and carbon dioxide is a further limitation.
• Statement 3 is correct. PET is among the most widely recycled polymers, mechanically reprocessed into fibre for textiles, into sheet and strapping, and back into bottles, and chemical depolymerisation routes exist as well.
• Statement 4 is incorrect on elementary grounds. PET is a hydrocarbon polymer, so its combustion necessarily yields carbon dioxide, and incineration of plastics is therefore a source of greenhouse gas, quite apart from the other pollutants involved.
• Statements 1 and 3 hold, giving (a).
• Options (b), (c) and (d) each rest on statement 2 or statement 4, and statement 4's chemical impossibility gives a candidate a secure elimination route.

B cells and T cells are the lymphocytes of the adaptive immune system, and their defining role is defence against pathogens. B cells mature in the bone marrow and, on activation, differentiate into plasma cells secreting antibody against a specific antigen, giving humoral immunity, while some persist as memory cells. T cells mature in the thymus, the cytotoxic subset killing cells that display foreign antigen, as virus infected cells do, and the helper subset coordinating the response by activating B cells and macrophages, which is cell mediated immunity.

• Option (d) captures this and is correct.
• Option (a) is wrong as a description of their role: B cells do produce the IgE that mediates allergic reactions, but that is the immune system misdirected against a harmless substance rather than protection from allergens.
• Option (b) is wrong because the relief of pain and inflammation is the action of pharmacological agents, and lymphocyte activity in fact drives inflammation rather than resolving it.
• Option (c) is wrong and inverts the function; regulatory T cells do restrain the response to prevent autoimmunity, but that is one specialised subset and not the role of B and T cells generally.

• Statement 1 is incorrect, and decisively so. Nanoscale particles are abundant in nature and always have been: volcanic ash and sea spray aerosols, soot from combustion and forest fire, clay mineral colloids in soil and water, and biological structures such as ferritin and viruses all fall in the nanometre range. Engineered nanoparticles are a recent addition to a natural population, not a new class of matter.
• Statement 2 is correct. Nanoparticles of titanium dioxide and zinc oxide are used in sunscreens and other cosmetics, where reducing the particle size preserves the ultraviolet blocking action while removing the opaque white film that larger particles leave on the skin.
• Statement 3 is correct as the key treats it. Nanoparticles released from commercial products into the environment raise recognised safety concerns, since their small size and large surface area allow them to cross biological barriers and interact with tissues in ways the same material in bulk does not, and silver and titanium dioxide nanoparticles have attracted particular attention.
• Statements 2 and 3 holding, (d) is correct; options (a) and (c) accept the false claim about nature, and (b) drops the well established cosmetic use.

DNA barcoding identifies an organism by sequencing a short, standardised region of its genome and matching that sequence against a reference library, the mitochondrial cytochrome c oxidase I gene serving for animals and chloroplast regions such as rbcL and matK for plants. The method answers the question of what an organism is, and its capabilities follow from that.

• Statement 1 is incorrect, since the barcode sequence is a property of the species and does not change as an individual ages; age is estimated by other means altogether, growth rings, otoliths, skeletal or dental features, or in some contexts telomere length or epigenetic clocks, none of which is barcoding.
• Statement 2 is correct and is the method's central application, resolving cryptic species and morphologically indistinguishable specimens, and identifying material such as larvae, fragments or processed parts that cannot be identified by appearance.
• Statement 3 is correct and follows directly: because a barcode can be recovered from fragmentary tissue, the technique is used in food authentication to detect substituted or adulterated ingredients and undeclared species in processed products.
• Statements 2 and 3 holding, (d) is correct; options (a) and (c) accept the age determination claim, and (b) drops the method's principal use.

• Statement I is correct. Coal supplies roughly seventy per cent of India's electricity generation while nuclear power contributes around three per cent, notwithstanding domestic uranium in Jharkhand and Andhra Pradesh.
• Statement II is incorrect and is the crux of the question. Power reactors run on low enriched uranium of about three to five per cent uranium-235, and India's indigenous pressurised heavy water reactors use natural uranium at 0.7 per cent because heavy water moderation removes the need for enrichment altogether. Enrichment to sixty per cent and above belongs to the weapons and high performance research reactor domain, not electricity generation. Since Statement I is correct and Statement II is false, (c) follows.
• Options (a) and (b) require Statement II to be true, and (d) inverts the truth values.

All three describe recognised classes of extremophiles.

• Statement 1 is correct. Hyperthermophilic archaea at deep sea hydrothermal vents, such as Pyrolobus fumarii and Methanopyrus, grow above 100 degrees Celsius because the high hydrostatic pressure at those depths raises the boiling point of water and their proteins and membranes are thermostable.
• Statement 2 is correct. Psychrophiles grow in polar brines and sea ice at sub zero temperatures, aided by antifreeze proteins and by the depressed freezing point of saline water.
• Statement 3 is correct. Acidophiles such as Acidithiobacillus and Picrophilus thrive below pH 3 in acid mine drainage and volcanic springs, maintaining near neutral cytoplasm through proton pumping.

Hence (c), and (a), (b) and (d) each require one of these well documented groups to be denied.

• Statement 1 is correct. Carbon fibre reinforced polymers combine very high specific strength and stiffness with low density and fatigue resistance, which is why they are used in aircraft primary structures, in automotive body panels and chassis components, and in wind turbine blades and pressure vessels.
• Statement 2 is incorrect. Carbon fibre composites are recycled at commercial scale, principally by pyrolysis in which the polymer matrix is thermally decomposed and the fibres recovered, and also by solvolysis and mechanical grinding. The recovered fibres are shorter and lose some strength, so the process is downcycling rather than closed loop recovery, but recycling certainly occurs. Only statement 1 stands, giving (a).
• Options (b) and (c) require the recyclability claim to be denied, and (d) denies an obvious use.

• Pairs 1 and 2 are straightforwardly swapped, which is the whole design of the question. Cepheids are variable stars that brighten and dim with a regular period, and because the period is tightly related to intrinsic luminosity through the Leavitt law they serve as standard candles for measuring extragalactic distances. Nebulae are the giant clouds of dust and gas. So pair 1 is wrong and pair 2 is wrong, each carrying the other's description.
• Pair 3 is accepted as correct. A pulsar is indeed a neutron star produced by the core collapse of a massive star that has exhausted its nuclear fuel. Only one pair matches, giving (a).

Both statements are reversed, which makes this a straightforward elimination once the basic distinction is held.

• Statement 1 is incorrect. A ballistic missile is rocket powered only during the boost phase and thereafter follows a free ballistic trajectory through mid course and re entry, reaching hypersonic speeds. A cruise missile is air breathing and jet propelled through most of its flight, sustaining powered aerodynamic flight at low altitude, and many are subsonic.
• Statement 2 is likewise reversed. Agni-V is a solid fuelled long range ballistic missile in the intercontinental class, while BrahMos is a supersonic cruise missile with a ramjet sustainer. Neither statement stands, giving (d).

All three describe established or demonstrated uses of hydrogen, and green hydrogen differs from other hydrogen only in its production route, namely electrolysis powered by renewable electricity, not in its end use chemistry.

• Statement 1 is correct, hydrogen internal combustion engines having been demonstrated in cars, buses and generator sets, burning hydrogen in a modified spark ignition engine.
• Statement 2 is correct, hydrogen being blended into natural gas grids at low percentages for heating and power, with trials in India and abroad.
• Statement 3 is correct, the proton exchange membrane fuel cell producing electricity directly from hydrogen and oxygen with water as the only exhaust, which is the basis of fuel cell electric vehicles. Hence (c). The question is generous in that each option is a well publicised application, and no elimination is needed.

The term is built from its two parts. Metagenomics is the sequencing of genetic material recovered directly from an environmental sample rather than from a cultured or captured organism, and aerial specifies air as the medium. Aerial metagenomics therefore means filtering air and sequencing the environmental DNA it carries in shed skin, hair, spores, pollen and droplets, which allows an inventory of species present in a habitat without observing or trapping any of them.

• Option (b) confuses aerial with avian, a trap resting on the word association with birds.
• Option (c) describes remote biological sampling of blood, which involves neither air as a medium nor metagenomic sequencing.
• Option (d) describes drone assisted field sampling, which uses aerial platforms but collects conventional physical samples from land and water rather than DNA from the air itself.

Microsatellites, also called short tandem repeats, are stretches of DNA in which a motif of one to six base pairs is repeated in tandem. They mutate rapidly by replication slippage, so the number of repeats at a locus varies greatly between individuals, and they are co dominant and distributed throughout the genome. That high polymorphism makes them standard markers for individual identification in forensic DNA profiling, for parentage and population genetics, and for inferring relatedness and divergence among populations and closely related species, which is what (a) describes.

• Option (b) concerns growth factors and differentiation signals in stem cell biology, unrelated to repeat markers.
• Option (c) concerns tissue culture and vegetative propagation techniques.
• Option (d) concerns clinical trial methodology and pharmacology.

Hence (a).

• Statement 1 is incorrect. An RTG is not a reactor of any size. It contains no chain reaction, no criticality and no control mechanism. It converts the heat of spontaneous radioactive decay directly into electricity through thermocouples using the Seebeck effect.
• Statement 2 is correct. RTGs power onboard systems on missions where sunlight is too weak or intermittent for photovoltaics, as on Voyager, Cassini, New Horizons, Curiosity and Perseverance.
• Statement 3 is correct. Plutonium-238 is produced by neutron irradiation of neptunium-237, itself a by product of the reactor operations and reprocessing associated with weapons programmes, and its 87.7 year half life and alpha emission make it well suited to RTGs. Hence 2 and 3 only, which is (b).
• Options (a), (c) and (d) all retain the fission reactor error.

• Statement-I is incorrect. Massive giant stars live far shorter lives than low mass dwarfs. A massive O or B type star may last only a few million years, whereas a red dwarf can burn for hundreds of billions of years, longer than the present age of the universe.
• Statement-II is correct. Higher mass means higher core temperature and pressure, and since the CNO cycle rate scales very steeply with temperature, giant stars consume their hydrogen at an enormously greater rate. The two statements together illustrate that the correct inference runs opposite to Statement-I. Greater fuel consumption per unit time, despite the larger fuel reserve, gives a shorter main sequence lifetime, since lifetime scales roughly as mass divided by luminosity and luminosity rises as a high power of mass. Hence (d).
• Options (a) and (b) require Statement-I to be true, and (c) inverts both truth values.

Nitric oxide is synthesised in the vascular endothelium from L arginine by nitric oxide synthase. It diffuses into adjacent smooth muscle, activates guanylate cyclase, raises cyclic GMP and produces relaxation, that is vasodilation and increased blood flow. Its identification as the endothelium derived relaxing factor won the 1998 Nobel Prize in Physiology or Medicine, and it is the mechanism through which nitroglycerine relieves angina.

• Option (b) is wrong because nitrous oxide is an inhaled anaesthetic and laughing gas, administered externally and not synthesised as a signalling molecule in the body.
• Option (c) is wrong because nitrogen dioxide is a reddish brown atmospheric pollutant from combustion, an irritant rather than a physiological messenger.
• Option (d) is wrong because nitrogen pentoxide is an unstable laboratory oxidising agent with no biological role.

In a proton exchange membrane fuel cell, hydrogen is oxidised at the anode to protons and electrons, the protons cross the membrane, the electrons do external electrical work, and at the cathode oxygen combines with protons and electrons to form water. The only tailpipe product is therefore water, emitted chiefly as vapour along with warm air, which is why these vehicles are described as zero emission at the point of use.

• Option (a) is wrong because hydrogen peroxide can appear only as a transient and undesirable intermediate from incomplete oxygen reduction, and it is a degradation problem for the membrane rather than an emission.
• Option (b) is wrong because the hydronium ion exists within the hydrated membrane as the proton carrier and is not emitted.
• Option (c) is wrong because oxygen is consumed as the oxidant at the cathode, not produced.

Pumped storage hydropower uses surplus off peak or surplus renewable electricity to pump water from a lower reservoir to an upper reservoir, and releases it through turbines when demand or price is high. It is the dominant form of grid scale long duration energy storage worldwide, offering discharge over many hours and a service life measured in decades, which is why it is central to integrating variable solar and wind generation.

• Option (a) is wrong because terraced field irrigation is a soil and water conservation practice with no storage and generation cycle.
• Option (b) is wrong because lift irrigation pumps water for agricultural use and does not recover the energy, so it is a consumer rather than a store of electricity.
• Option (d) is wrong because rainwater harvesting captures precipitation for water supply and recharge, with no energy dimension at all. The distinguishing feature of pumped storage is that the pumping energy is deliberately recovered.

The metaverse denotes an interoperable network of persistent three dimensional virtual environments accessed simultaneously by large numbers of users, in which digital ownership of virtual land, avatars and items can be asserted, frequently through blockchain based tokens. Every element of the stem, interoperability, three dimensionality, simultaneous mass access and property rights over virtual items, is part of the standard definition.

• Option (a) is wrong because big data analytics refers to techniques for extracting patterns from very large datasets and has no spatial or ownership dimension.
• Option (b) is wrong because cryptography is the science of securing information, and while it underpins the token systems used for virtual property, it is not the environment itself.
• Option (d) is wrong because virtual matrix is not an established technical term and functions here purely as a distractor.

Every statement is universally quantified by the word all, and a single counterexample defeats each.

• Statement I is incorrect: fixed-wing UAVs generate lift from forward airspeed over the wing and cannot descend vertically under control, requiring a runway, a parachute, a net or a belly landing, which is why hybrid VTOL configurations were developed.
• Statement II is incorrect for the same aerodynamic reason: sustained hovering requires thrust directed against gravity from rotors, so rotary-wing and multirotor platforms hover while fixed-wing aircraft must maintain forward speed above stall and can at best loiter in a circle.
• Statement III is incorrect: while small multirotors are typically battery powered, larger and longer-endurance UAVs use internal combustion or turbine engines, and hydrogen fuel cells and solar power are also employed, with energy density being the binding constraint since batteries cannot yet deliver the endurance that military and surveillance roles demand. None of the statements holds, giving (d).
• Options (a), (b) and (c) each require at least one universal claim to survive, and the fixed-wing counterexample alone defeats the first two. Extreme quantifiers of this kind are a reliable signal in Prelims.

In a lithium-ion cell the cathode is a lithium metal oxide and the anode is almost always graphite, and this division is the whole content of the question. Cobalt, lithium and nickel are cathode constituents: the dominant chemistries are nickel manganese cobalt oxide and nickel cobalt aluminium oxide, alongside lithium iron phosphate which dispenses with nickel and cobalt, and lithium is present in every cathode formulation since it supplies the ions that shuttle during cycling. Graphite is the anode material, chosen because its layered structure intercalates lithium ions reversibly between graphene planes at a potential close to that of lithium metal without the dendrite formation that plagues lithium metal anodes. Three elements therefore belong to the cathode, giving (c).

• Option (d) requires graphite to be counted as a cathode material, which reverses the electrode assignment.
• Options (a) and (b) understate, and would require excluding one of the three genuine cathode elements. The practical significance is that cobalt and nickel supply concerns drive cathode chemistry away from cobalt-rich formulations, while graphite supply is a separate and equally concentrated bottleneck on the anode side.

All three are high explosives used in military munitions, giving (b). They belong to the class of nitrogen-rich energetic materials, and the family also includes the more familiar RDX and TNT. The distinctions among them concern the balance between energy release and stability: some members of the class are valued for high detonation performance, while others are developed as insensitive munitions, meaning they resist accidental initiation by shock, fire or fragment impact during storage and handling, which is a major safety consideration for naval and aircraft magazines.

• Option (a) is wrong because refrigerant replacements for hydrofluorocarbons are hydrofluoroolefins, ammonia, carbon dioxide and hydrocarbons, an entirely unrelated chemistry driven by the Kigali Amendment.
• Option (c) is wrong because cruise missile propulsion uses conventional liquid hydrocarbon fuel in a turbojet or turbofan, and these compounds would sit in the warhead rather than the fuel tank.
• Option (d) is wrong for a related reason: solid rocket propellants are formulated from an oxidiser such as ammonium perchlorate with a metallic fuel and a polymeric binder, and although some energetic materials appear as propellant additives, that is not the defining characteristic of this group.

• Statement I is correct: Majorana 1 was announced as a quantum processing chip built on a topological approach, using engineered structures intended to host Majorana zero modes so that quantum information is stored non-locally and is therefore intrinsically more resistant to decoherence, which is the central obstacle to scaling quantum computers.
• Statement II is incorrect and is the sole discriminator: the chip was announced by Microsoft, which has pursued the topological qubit route for years, not by Amazon Web Services, whose quantum efforts run under a different programme and chip lineage.
• Statement III is correct and is a definitional matter: artificial intelligence is the broadest category, machine learning is the subset of approaches that learn patterns from data rather than following explicitly programmed rules, and deep learning is in turn the subset of machine learning that uses multi-layered neural networks to learn hierarchical representations.
• Statements I and III hold, giving (c).
• Options (a) and (d) both retain the wrong attribution, and option (b) drops the accurate statement about the chip while keeping the false one. A candidate certain only of the nesting relationship in Statement III could narrow the field to (b), (c) and (d).

• Statement I is correct: monoclonal antibodies are laboratory-produced immunoglobulin proteins, classically generated by hybridoma technology in which an antibody-producing B cell is fused with a myeloma cell to create an immortal clone secreting a single antibody specificity, and now increasingly by recombinant and humanised methods. The term monoclonal captures exactly this, that all molecules derive from one clone and are therefore identical, in contrast to the polyclonal mixture produced by a natural immune response.
• Statement II is correct: their therapeutic action rests on binding a chosen antigen with high specificity, which can neutralise a pathogen directly by blocking entry, or recruit immune effector functions such as complement activation and antibody-dependent cellular cytotoxicity.
• Statement III is correct: the monoclonal antibody m102.4 has been used against Nipah virus, including on a compassionate basis during outbreaks in Kerala, and monoclonals have also been deployed against Ebola, respiratory syncytial virus and, during the pandemic, SARS-CoV-2. All three hold, giving (d).
• Options (a), (b) and (c) each drop one accurate statement, with no error present in any of the three to justify exclusion.

All three statements are false, giving (d), and each is phrased as a universal negative that a single counterexample destroys.

• Statement I is incorrect: seawater is the most virus-rich environment known, holding on the order of ten million virus particles per millilitre, and marine viruses are a major ecological force, lysing bacterial and phytoplankton populations and thereby driving the viral shunt that recycles organic carbon and nutrients in surface waters.
• Statement II is incorrect: bacteriophages are viruses that specifically infect bacteria, they were central to the foundational experiments of molecular biology including the Hershey and Chase demonstration that DNA is the genetic material, and phage therapy is under renewed investigation as antibiotic resistance spreads.
• Statement III is incorrect: altering host transcription is fundamental to how viruses replicate, since they must divert host machinery to make viral products, and some go further by integrating into the host genome, as retroviruses do, or by driving oncogenesis through sustained transcriptional dysregulation, as human papillomavirus does. None holds, giving (d).
• Options (a), (b) and (c) each require at least one absolute negation to survive, and none can.

• Statement I is correct: the scheme, launched in February 2024 and implemented by the Ministry of New and Renewable Energy, targets the installation of rooftop solar systems in one crore residential households, supported by central financial assistance graded by system capacity and by collateral-free concessional loans, with households receiving free electricity up to a specified monthly consumption and able to sell surplus power to the distribution company.
• Statement II is correct: the scheme provides for training at grassroots level in installation, operation, maintenance and repair of rooftop solar systems, which addresses the practical constraint that a dispersed residential rollout of this scale needs a distributed technician base rather than a few large contractors.
• Statement III is correct: the capacity building component envisages the creation of more than three lakh skilled personnel through fresh skilling and upskilling, with a substantial share as certified solar photovoltaic technicians. All three hold, giving (d).
• Options (a), (b) and (c) each drop one accurate component. The design point worth noting is that the scheme couples a demand-side subsidy with a supply-side skilling programme, since installation capacity rather than panel availability is usually the binding constraint on rooftop deployment.

• Statement I is correct: rare earth elements are essential to display manufacture, with europium providing red emission, terbium green, and yttrium serving as the host lattice in many phosphor compositions, alongside cerium and gadolinium in related applications.
• Statement II is correct: several lanthanides are strongly luminescent, and Statement II supplies the reason for Statement I, so the explanatory link holds and the answer is (a). The physical basis is worth stating precisely. Emission in the lanthanides arises from transitions between four f orbitals, which lie inside the filled five s and five p shells and are therefore shielded from the surrounding crystal field. Two consequences follow: the emission occurs at sharply defined wavelengths largely independent of the host material, which gives displays their colour purity, and the transitions are formally forbidden by the Laporte selection rule, which makes them slow and the excited states long-lived.
• Options (c) and (d) each reject one accurate statement.
• Option (b) concedes both but denies the causal connection, which cannot stand, since the luminescent property is precisely why these elements are chosen for screens.

The stem asks which statements are not correct, so the reasoning must be inverted before matching to the options.

• Statement I is not correct: the National Rail Plan sets its horizon at 2030, not 2028, with a stated aim of creating a future ready railway system and raising the rail share of freight modal traffic.
• Statement II is not correct: Kavach was developed indigenously by the Research Designs and Standards Organisation together with Indian firms, and is presented as a Made in India train protection system, so the attribution to German collaboration is wrong.
• Statement III is in fact correct, and therefore does not belong in the answer: Kavach uses RFID tags fixed to the track in station sections and at signals, which the locomotive reader uses to establish position, working alongside radio communication between the loco unit, the stationary unit and other locomotives to enforce automatic braking when a signal is passed at danger or a speed restriction is exceeded. The statements that are not correct are I and II, giving (a).
• Option (d) wrongly rejects the accurate RFID description, and options (b) and (c) each mix one accurate statement into the set of incorrect ones.

GAGAN is a satellite based augmentation system developed jointly by ISRO and the Airports Authority of India, which uses a network of reference stations to measure errors in the GPS signal arising from ionospheric delay, satellite clock drift and orbital uncertainty, computes corrections at a central facility, and broadcasts them through geostationary satellites.

• Statement I is correct: the system improves both accuracy, by correcting these errors, and integrity, by warning users promptly when the signal should not be trusted, and integrity is the more critical property for aviation since a wrong position believed to be right is far more dangerous than a known loss of service.
• Statement II is correct: reliable satellite based approach guidance permits more direct routing, reduced separation and precision approaches at airfields lacking ground based instrument landing systems, which improves the uniformity and quality of air traffic management.
• Statement III is incorrect, and it is the intended trap. The corrected signal is available to any receiver in the coverage area, and applications extend to railways, maritime navigation, road transport, precision agriculture, surveying and disaster management.
• Statements I and II hold, giving (d).
• Options (a) and (b) retain the exclusivity claim, and option (c) discards the air traffic benefit.

• Statement I is correct: the AI Action Summit was held at the Grand Palais in Paris in February 2025, co-chaired by France and India, and it was the third in the sequence that began with the AI Safety Summit at Bletchley Park in November 2023 and continued with the Seoul Summit in May 2024. The shift of vocabulary across the three, from safety at Bletchley to action at Paris, reflects a widening of the agenda from catastrophic risk towards access, development and public interest applications, which is the context in which India's co-chairing is significant.
• Statement II is incorrect and is the decisive point: the United States and the United Kingdom declined to sign the declaration on inclusive and sustainable artificial intelligence, while some sixty other participants endorsed it. The reported reasons differed, with concerns expressed about the effect of the framing on innovation and about national security language, but the fact of non-signature by both was widely reported at the time. Only I holds, giving (a).
• Options (b) and (c) accept the signature that did not occur, and option (d) wrongly rejects the accurate account of the summit lineage and co-chairing.

• Statement 1 is correct and is the definition of the field, since gene therapy either supplies a working copy of a defective gene, silences a harmful one, or edits the sequence at a specific site so that the underlying genetic cause rather than the symptom is addressed.
• Statement 2 is correct, since delivery is the central engineering problem and the two dominant answers are viral vectors, chiefly adeno associated virus and lentivirus stripped of their capacity to replicate, and lipid nanoparticles, which encapsulate nucleic acid in an ionisable lipid shell and are the technology familiar from messenger RNA vaccines.
• Statement 3 is incorrect and is the eliminator. The whole point of the technology is that intervention is targeted, at one gene or one locus, and altering an entire genome of three billion base pairs is neither the aim nor within reach, and would be catastrophic if attempted. Hence 1 and 2 and (c) is correct. (a) drops the well established delivery methods, and (b) and (d) accept a claim that contradicts the targeted nature of the therapy.

• Statement 1 is treated as correct. A language model computes a probability distribution over the next token given everything before it, and selecting the highest probability candidate, known as greedy decoding, is the textbook description of how text is then produced.
• Statement 2 is correct and describes training rather than generation, since the parameters are fitted by gradient descent on a loss function that measures how far the predicted distribution sits from the observed next token, so the entire training process is mathematical optimisation to reduce prediction error.
• Statement 3 is incorrect and is the eliminator. A model learns the statistical regularities of its training corpus, and any imbalance, stereotype or skew in that corpus is learned along with everything else, so bias is an expected property rather than an aberration.

Hence 1 and 2 and (b) is correct, while (a) drops the accurate account of training and (c) and (d) accept the claim of unbiased output.

• Statement 1 is correct and states the two pillars of the technology. Shaping deflects incident energy away from the transmitter so that little returns to the receiver, which reduces the radar cross section, and radar absorbing material converts a further part of the incident energy into heat within a lossy ferrite or carbon loaded coating.
• Statement 2 is correct and follows from the physics of the first. Shaping and absorbing coatings are optimised for the centimetric wavelengths of fire control radars, so when the wavelength becomes comparable to major structural features of the airframe, as with metre wave VHF and UHF radars, the scattering regime changes and returns rise sharply, which is why low frequency surveillance radars are the standard counter stealth measure.
• Statement 3 is incorrect and is the eliminator, since the objective is always to reduce the energy returned to the receiver, and a coating designed to increase scattering would defeat the entire purpose. Metamaterials are studied in this field precisely for the opposite reason, to guide waves around a body or absorb them over a wide band.

Hence 1 and 2 and (c) is correct, while (b) and (d) accept a statement whose verb points the wrong way.

• Statement 1 is incorrect and is the eliminator. The underwater locator beacon attached to a flight recorder is acoustic, not optical, emitting an ultrasonic pulse at about thirty seven and a half kilohertz once a second for around thirty days once immersed. The reason is physical rather than incidental, since sea water attenuates visible light within tens of metres while sound at that frequency propagates over kilometres, so a light beacon would be useless at ocean depths.
• Statement 2 is correct, because a modern installation captures cockpit audio through the cockpit voice recorder and hundreds to over a thousand flight parameters through the flight data recorder, and current combined units house both functions.
• Statement 3 is correct, since the crash survivable memory unit is the armoured core of the device, its stack of solid state memory boards wrapped in thermal insulation and sealed inside a shell of stainless steel or titanium to survive impact, a fire of about eleven hundred degrees Celsius for an hour and prolonged deep water pressure.

Hence 2 and 3 and (b) is correct, while (a), (c) and (d) all admit the light beacon claim.

• Statement 1 is incorrect and is the eliminator, because hydrogen produced by steam methane reforming with the resulting carbon dioxide captured and stored is blue hydrogen. The feedstock remains a fossil fuel and the emission reduction depends on the capture rate, so it is not green by definition. Green hydrogen is defined by the origin of the energy, not by the treatment of the exhaust.
• Statement 2 is correct and is that definition, namely electrolysis of water driven by renewable electricity, which yields hydrogen and oxygen with no carbon in the process chain at all.
• Statement 3 is correct, since the National Green Hydrogen Mission approved in January 2023 carries the stated targets of about five million tonnes of annual production capacity by 2030 together with abatement of nearly fifty million tonnes of greenhouse gas emissions a year.

Hence 2 and 3 and (b) is correct, while (a) and (d) accept the blue hydrogen description and (c) drops the mission target.

• Statement 1 is correct, since IN-SPACe was created in 2020 as a single window autonomous body under the Department of Space to authorise, promote and hand hold private activity in launch, satellites and ground segment, distinct from ISRO as operator and from NewSpace India Limited as the commercial arm.
• Statement 2 is correct, since the Agnibaan sub orbital technology demonstrator flown from Sriharikota in 2024 used the Agnilet engine, a single piece additively manufactured semi cryogenic engine, and that flight is credited as the first by a rocket powered by a single piece three dimensionally printed engine.
• Statement 3 is incorrect and is the eliminator, because Skyroot is an independent launch vehicle developer whose Vikram series it builds and flies itself, the Vikram S sub orbital flight of 2022 being India's first privately built rocket, and it neither develops nor supplies propellant for the GSLV, which is an ISRO vehicle using its own indigenous cryogenic stage.

Hence 1 and 2 and (c) is correct, while (b) and (d) accept the false Skyroot claim and (a) drops the Agnikul achievement.

• Statement 1 is incorrect and is the eliminator. Command and control links for drones operate in conventional radio bands, typically the very and ultra high frequency ranges and the industrial bands around two point four and five point eight gigahertz, with satellite links for long endurance platforms. Terahertz radiation is strongly absorbed by atmospheric water vapour and is limited to very short line of sight distances, which makes it unsuitable for a link to a command centre.
• Statement 2 is correct and is the defining feature of a swarm as opposed to a formation of individually piloted drones, since the drones share position and target information over a mesh network and reallocate tasks among themselves, so that the loss of one does not break the group.
• Statement 3 is correct, since spoofing, that is transmitting counterfeit satellite navigation signals stronger than the genuine ones so that the receiver computes a false position, is a standard soft kill counter unmanned aerial system technique alongside jamming, and it is attractive because it can redirect or land a drone without kinetic engagement.

Hence 2 and 3 and (b) is correct, while (a), (c) and (d) admit the terahertz claim.

• Statement 1 is incorrect and is the eliminator on chronology alone. The Human Genome Project was an international effort that ran from 1990 and was declared complete in 2003, producing a single composite reference sequence, whereas GenomeIndia was launched in 2020 as an independent Indian initiative, so a project begun seventeen years after another ended cannot be a part of it.
• Statement 2 is correct, since GenomeIndia is funded and coordinated by the Department of Biotechnology and executed through a consortium of about twenty Indian institutions led by the Indian Institute of Science.
• Statement 3 is correct, and it is also the reason the project exists. A single reference genome cannot represent a population of the size and endogamous structure of India's, so the aim is a catalogue of variation across diverse population groups, ten thousand whole genomes having been sequenced in the first phase, to support disease association studies and precision medicine for Indian populations.

Hence 2 and 3 and (b) is correct, while (a), (c) and (d) admit the false link to the Human Genome Project.

Both statements are correct, so (c) is the answer.

• Statement 1 reproduces the mission's own headline target, namely intermediate scale quantum computers in the range of fifty to one thousand physical qubits over eight years across several platforms including superconducting and photonic technologies. The wording physical qubits matters, since these are the raw hardware qubits before error correction rather than the far smaller number of logical qubits they would yield.
• Statement 2 is also correct, since the mission is organised around four thematic hubs distributed among academic and national research institutions, covering quantum computing, quantum communication, quantum sensing and metrology, and quantum materials and devices, each acting as a consortium lead rather than a single laboratory. With both statements sound, (a) and (b) each discard a correct one and (d) discards both.

• Statement 1 is incorrect and is the eliminator. The Deep Ocean Mission is a Ministry of Earth Sciences programme, implemented chiefly through the National Institute of Ocean Technology at Chennai, and the Ministry of Ports, Shipping and Waterways deals with ports, shipping and inland waterways rather than ocean science.
• Statement 2 is correct, since Matsya 6000 is a crewed submersible designed to carry three persons in a titanium alloy personnel sphere of about two point one metres internal diameter to a depth of six thousand metres, with an endurance of roughly twelve hours and seventy two hours of emergency reserve.
• Statement 3 is correct, since Samudrayaan is precisely the crewed submersible component of the Deep Ocean Mission and Matsya 6000 is the vehicle built for it, the mission's other components covering deep sea mineral exploration, ocean climate advisory services, marine biodiversity and an offshore energy and desalination demonstration.

Hence 2 and 3 and (b) is correct, while (a), (c) and (d) admit the wrong ministry.

The official key treats all three statements as correct, giving (a).

• Statement 1 is sound, since the mission as announced is an integrated shield combining air defence, ballistic missile defence and an offensive counter strike element rather than a purely defensive layer, which is what distinguishes it from an air defence programme alone.
• Statement 2 is sound and is essentially the stated rationale, that indigenous capability across detection, interception and response reduces dependence on external suppliers and therefore reinforces strategic autonomy.
• Statement 3 reflects the announced horizon of 2035 and the intention to extend protection beyond purely military assets to civilian and religious sites and centres of population. There is no option offering 1 and 2 while excluding 3 in a way that would be preferable, since (b) would require statement 3 to be false in substance and not merely loose in wording.

• Item 1 is correct, since the Su-30 MKI is built under licence by Hindustan Aeronautics Limited at Nashik from Russian design with progressively increasing indigenous content, and further batches have been ordered from the same line.
• Item 2 is correct, since the T-90 series is produced under licence at the Heavy Vehicles Factory at Avadi, and the T-90 Mk-III variant with an improved engine, thermal imaging and an automatic target tracker was sanctioned for manufacture there.
• Item 3 is incorrect and is the eliminator, since Akula class nuclear powered attack submarines are Russian built and have been operated by India only on lease, the INS Chakra arrangements being the examples, whereas India's own nuclear submarine construction is the indigenous Arihant class of ballistic missile submarines at Visakhapatnam. Hence 1 and 2 and (a) is correct. (b) admits the Akula, (c) drops the Avadi tank line, and (d) drops the Nashik aircraft line.

• Statements 1 and 2 are correct and statement 3 is the eliminator, so (c) is the answer.
• Statement 2 is the substantive point and can be reasoned rather than recalled, since the purpose of a national standard is precisely to fix common test methods and performance thresholds so that equipment bought by different agencies, the police, the paramilitary forces and the armed forces, meets a comparable specification and can be used and serviced across them.
• Statement 1 records the designation of that standard.
• Statement 3 fails on the attribution, since a national standard issued by the Bureau of Indian Standards is developed through its own sectional committees drawing on domestic technical expertise, in this case the Terminal Ballistics Research Laboratory of the Defence Research and Development Organisation at Chandigarh, and the addition of a named foreign research institute is the inserted error. A standard intended to secure indigenous procurement autonomy would not be co-developed with a foreign defence research body. (a) and (b) accept that attribution and (d) discards the interoperability rationale.

• Statements 1, 2 and 4 are correct, giving (c).
• Statement 1 describes transparency with integrity, since permissioned visibility to stakeholders is combined with tamper evidence because each block carries the hash of its predecessor.
• Statement 2 describes the distributed ledger itself, in which every participating node holds a full copy and the copies are reconciled continuously by the consensus mechanism.
• Statement 4 describes immutability, which follows from statement 2, because altering a past record would require recomputing every subsequent hash and imposing that revised chain on a majority of independent nodes.
• Statement 3 is the eliminator, and the error is a swapped definition. A consortium or federated blockchain is a permissioned chain governed jointly by a group of organisations rather than by one, and it is a variety of private blockchain. The description offered, a blend of public and private allowing selective data access, is the definition of a hybrid blockchain. (a), (b) and (d) each either admit that swapped definition or discard one of the three sound features.

• Statements 1 and 3 are correct, giving (a).
• Statement 1 is sound, since neodymium, praseodymium, dysprosium and terbium go into the high strength permanent magnets that drive robotic actuators, hard disk assemblies, satellite reaction wheels and electric traction motors, while other lanthanides serve in phosphors, lasers and catalysts.
• Statement 3 is sound, since the National Critical Mineral Mission was approved in January 2025 covering exploration, domestic and overseas acquisition, recycling and stockpiling.
• Statement 2 is wrong on the second name, because although China dominates mining with a large majority of world output, the countries following it are the United States, Myanmar and Australia, while India holds substantial monazite reserves but a very small share of actual mined production, and confusing reserves with output is the trap.
• Statement 4 is wrong on the count, because rare earth elements number seventeen, the fifteen lanthanides together with scandium and yttrium, which are grouped with them because they share ionic radius and chemical behaviour and occur in the same ores. (b) discards the applications statement, and (c) and (d) accept the count of thirteen.