Computing, AI and Communications

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.

• 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.

• 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.

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.

• 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 (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. 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.

• 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.

• 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.

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 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.

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.

• 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).

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.

• 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 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 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. 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.

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.

• 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.