Science and Technology: previous-year questions
185 real UPSC Prelims questions (2011–2026) with the official answer and a clear explanation. 50 of them came in the last five papers.
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Which of the following statements about DHRUV64 is/are correct ?
- 1. It is the third chip fabricated under the DIR-V Programme with an overall aim to enable the creation of microprocessors for India.
- 2. It is India’s first homegrown 1.0 GHz, 64-bit dual-core microprocessor.
Select the answer using the code given below :
Answer (c) & explanation
Both statements are correct (c). Statement 1 is right: DHRUV64, announced in December 2025 by C-DAC, is the third chip fabricated under the Digital India RISC-V (DIR-V) programme, after THEJAS32 and THEJAS64. Statement 2 is right: it is India's first homegrown 1.0 GHz, 64-bit dual-core microprocessor. So options (a), (b) and (d) fail.
Notice the technology: RISC-V is an open-source instruction set, so India can design chips without paying licence fees to owners of ARM or x86 designs. DHRUV64 targets 5G equipment, industrial automation, automotive and IoT uses. Next in line are the Dhanush chips. The India Semiconductor Mission (2021) supports the wider fab and assembly ecosystem.
Answer as per the official UPSC answer key.
Which one of the following pairs of semiconductor plants in India and their locations is not correctly matched ?
Answer (c) & explanation
The pair HCL-Foxconn : Madhya Pradesh is wrong (c). The HCL–Foxconn joint venture India Chip Ltd. was approved in 2025 near Jewar in Uttar Pradesh, close to the new airport, not in Madhya Pradesh. Option (a) is correct: CG Power with Renesas and STARS is building at Sanand, Gujarat. Option (b) is correct: Tata's assembly and test unit is at Jagiroad, Assam. Option (d) is correct: SiCSem's silicon carbide fab is in Odisha.
Notice the anchor project: Tata and PSMC of Taiwan are building India's first big fab at Dholera, Gujarat, and Micron's assembly unit is at Sanand. These come under the India Semiconductor Mission (2021), which offers about 50% fiscal support.
Answer as per the official UPSC answer key.
Which of the following statements with regard to genetic medicine is/are correct ?
- 1. Genetic medicines correct/compensate for the faulty genes responsible for disease.
- 2. Engineered viruses and lipid nanoparticles are used as carriers of the genetic medicine.
- 3. Genetic medicines alter the entire DNA sequence.
Select the answer using the code given below :
Answer (c) & explanation
Statements 1 and 2 are correct (c). Statement 1 is right: genetic medicines correct or make up for the faulty genes behind a disease, by adding a working copy, silencing a bad gene or editing a small stretch. Statement 2 is right: they are delivered by engineered viruses, such as AAV, or lipid nanoparticles, the carrier used in mRNA vaccines. Statement 3 is wrong: no therapy rewrites the entire genome. So options (a), (b) and (d) fail.
Notice India's progress: its first home-grown CAR-T cell therapy for cancer, NexCAR19 (2023), and a successful gene therapy trial for haemophilia at CMC Vellore. CRISPR-based Casgevy was the first approved gene-editing cure, for sickle cell disease.
Answer as per the official UPSC answer key.
Which of the following statements with regard to India’s indigenous new high resolution weather model, the ‘Bharat Forecast System,’ is/are correct ?
- 1. Its objective is to generate forecasts at the Panchayats cluster level.
- 2. It was developed by IIT Delhi.
Select the answer using the code given below :
Answer (a) & explanation
Only statement 1 is correct (a). Statement 1 is right: the Bharat Forecast System (BFS), launched in May 2025, runs at about 6 km resolution, fine enough for forecasts at the level of panchayat clusters. Statement 2 is wrong: it was developed by the Indian Institute of Tropical Meteorology (IITM), Pune, and runs on the Arka supercomputer, not at IIT Delhi. So options (b), (c) and (d) fail.
Notice the advance: earlier global models ran at about 12 km, so BFS gives much sharper local forecasts of heavy rain and cyclones. It is among the world's highest-resolution operational models. IITM works under the Ministry of Earth Sciences, alongside the IMD. Better forecasts help farmers and disaster management.
Answer as per the official UPSC answer key.
Which of the following statements with regard to Large Language Models (LLMs) used in machine learning is/are correct ?
- 1. LLMs assign probabilities to the next possible words and then pick the one with the highest probability.
- 2. LLMs process data through mathematical optimization to minimise prediction errors.
- 3. LLMs produce unbiased outputs.
Select the answer using the code given below :
Answer (b) & explanation
Statements 1 and 2 are correct (b). Statement 1 is right: a Large Language Model predicts the next word, or token, by giving every candidate a probability, and then picks a likely one. Statement 2 is right: it learns by optimisation, adjusting billions of weights to reduce prediction error on its training text. Statement 3 is wrong: because it learns from human text, it can repeat human bias. So options (a), (c) and (d) fail.
Notice the related risks: hallucination, where an LLM confidently gives false facts, and deepfakes made by generative AI. India's IndiaAI Mission backs Indian-language models such as BharatGen and Sarvam. The "T" in GPT stands for Transformer, the design behind modern LLMs.
Answer as per the official UPSC answer key.
Which of the following statements regarding the features of blockchain technology are correct ?
- 1. Records stored in the database may be made visible to relevant stakeholders without risk of alteration.
- 2. Copies of the entire database are stored on multiple computers on a network, syncing within seconds.
- 3. Consortium blockchain is a blend of public and private blockchains allowing selective data access.
- 4. Mathematical algorithms make it impossible to change or delete any data once recorded and accepted.
Select the answer using the code given below :
Answer (c) & explanation
Statements 1, 2 and 4 are correct (c). A blockchain is a shared record of transactions copied across many computers. Statement 1 is right: records can be shown to stakeholders without risk of alteration. Statement 2 is right: copies of the whole ledger sit on many nodes and sync quickly. Statement 4 is right: cryptographic hashing links each block to the last, so accepted data cannot be changed or deleted. Statement 3 is wrong: a blend of public and private is a hybrid blockchain; a consortium blockchain is run by a group of organisations. So options (a), (b) and (d) fail.
Notice uses in India: land records, supply chains, and the RBI's e-rupee pilots. Bitcoin (2009) was the first public blockchain.
Consortium and hybrid both sound like a mix. Consortium means many owners; hybrid means a mix of public and private.
Answer as per the official UPSC answer key.
Which of the following statements with regard to stealth technology is/are correct ?
- 1. Stealth objects have a very small radar cross-section and are coated with Radar Absorbing Material.
- 2. Stealth objects can be detected using specific frequencies.
- 3. Stealth objects are coated with metamaterials to increase the scattering of electromagnetic radiation.
Select the answer using the code given below :
Answer (c) & explanation
Statements 1 and 2 are correct (c). Statement 1 is right: stealth aircraft cut their radar cross-section through shape and radar-absorbing material (RAM). Statement 2 is right: they are tuned against common radar bands, so low-frequency radars, such as VHF, can still pick them up. Statement 3 is wrong: metamaterial coatings are meant to absorb or bend waves away, reducing the echo, not increasing scattering. So options (a), (b) and (d) fail.
Notice examples: the US F-35 and B-2, China's J-20, and Russia's Su-57. India's AMCA fifth-generation fighter is planned to be stealthy. Stealth also cuts infrared heat and noise signatures. Other counters include passive radar and multi-static radar networks.
Statement 3 uses a real term, metamaterials, but gives them the opposite purpose.
Answer as per the official UPSC answer key.
Which of the following statements with regard to Black Boxes used in modern aircrafts is/are correct ?
- 1. They carry a beacon emitting red light pulses to facilitate underwater detection.
- 2. They record both the cockpit voice and flight data.
- 3. Their memory units are made using either stainless steel or titanium.
Select the answer using the code given below :
Answer (b) & explanation
Statements 2 and 3 are correct (b). Statement 2 is right: the "black box" is really two orange recorders, the cockpit voice recorder and the flight data recorder. Statement 3 is right: their crash-survivable memory sits in stainless steel or titanium shells. Statement 1 is wrong: under water, the locator beacon sends out ultrasonic pulses, about 37.5 kHz, not red light. So options (a), (c) and (d) fail.
Notice why they are orange: to be easy to spot in wreckage. The beacon works for about 30 to 90 days. Black boxes were key in probing the Air India Ahmedabad crash (June 2025); India's AAIB read its data at a new lab in Delhi. Newer rules call for 25-hour voice recording.
Answer as per the official UPSC answer key.
Consider the following statements with regard to involvement of private entities in India’s space programme :
- 1. The Indian National Space Promotion and Authorisation Centre (IN-SPACe) is an autonomous agency formed to facilitate participation of private entities.
- 2. Agnikul Cosmos launched the world’s first flight using 3D-printed rocket engine.
- 3. Skyroot Aerospace has developed liquid fuel for GSLV.
Which of the statements given above is/are correct ?
Answer (c) & explanation
Statements 1 and 2 are correct (c). Statement 1 is right: IN-SPACe (2020) is the single-window, autonomous body under the Department of Space that authorises private space activity. Statement 2 is right: Agnikul's Agnibaan SOrTeD (May 2024) flew on the world's first single-piece 3D-printed semi-cryogenic engine. Statement 3 is wrong: Skyroot builds its own Vikram rockets; it does not make fuel for ISRO's GSLV. So options (a), (b) and (d) fail.
Notice Skyroot's milestone: Vikram-S (2022) was India's first privately built rocket to reach space. The Indian Space Policy, 2023 opened all space activities to private firms, and 100% FDI is allowed in parts of the sector. NSIL is ISRO's commercial arm.
Answer as per the official UPSC answer key.
Which of the following statements with regard to drone swarms is/are correct ?
- 1. They use Terahertz band of frequency to communicate with the command centre.
- 2. Individual drones in the swarm can communicate with other drones in the swarm.
- 3. GPS Spoofing is a commonly used technique to counter drone swarm attack.
Select the answer using the code given below :
Answer (b) & explanation
Statements 2 and 3 are correct (b). Statement 2 is right: in a swarm, the drones talk to each other and share tasks, so the group keeps working even if some are lost. Statement 3 is right: defenders often jam or spoof GPS to send them off course. Statement 1 is wrong: swarms usually use ordinary radio bands; terahertz links are still experimental and short-range. So options (a), (c) and (d) fail.
Notice other counters: laser weapons, like DRDO's directed-energy systems, anti-drone guns and net systems. India showed a 75-drone swarm at the 2021 Army Day parade. Drone wars in Ukraine and during Operation Sindoor (2025) showed how cheap drones can overwhelm costly defences.
Answer as per the official UPSC answer key.
Which of the following statements with regard to GenomeIndia Project is/are correct ?
- 1. It is a part of the Human Genome Project.
- 2. The project is funded by the Department of Biotechnology (DBT), Government of India.
- 3. Its primary aim is to build a catalogue of genetic diversity of the Indian population.
Select the answer using the code given below :
Answer (b) & explanation
Statements 2 and 3 are correct (b). Statement 2 is right: GenomeIndia (2020) is funded by the Department of Biotechnology. Statement 3 is right: it sequenced 10,000 genomes from many Indian communities to build a catalogue of the country's genetic variation, and the data was released in 2025. Statement 1 is wrong: the international Human Genome Project was a separate effort that ended in 2003. So options (a), (c) and (d) fail.
Notice the uses: finding gene variants behind diseases common in India, such as sickle cell and thalassaemia, and building personalised medicine. The data is stored at the Indian Biological Data Centre in Faridabad. A larger follow-up aims to sequence one million genomes.
Answer as per the official UPSC answer key.
Which of the following statements with regard to the National Quantum Mission (NQM) is/are correct ?
- 1. It aims at developing intermediate-scale quantum computers with 50-1000 physical qubits.
- 2. Its implementation includes setting up of four Thematic Hubs (T-Hubs) in academic and national R&D institutes across India.
Select the answer using the code given below :
Answer (c) & explanation
Both statements are correct (c). Statement 1 is right: the National Quantum Mission (2023, under the DST) aims at quantum computers of 50–1,000 physical qubits within eight years. Statement 2 is right: it has four T-Hubs: computing at IISc Bengaluru, communication at IIT Madras, sensing and metrology at IIT Bombay, and materials and devices at IIT Delhi. So options (a), (b) and (d) fail.
Notice the budget: about ₹6,000 crore from 2023-24 to 2030-31. The mission also aims at secure quantum communication over 2,000 km between cities, and satellite-based quantum links. India joined a handful of nations, like the USA, China and France, with such a dedicated mission.
Answer as per the official UPSC answer key.
Which of the following statements with regard to India’s Deep Ocean Mission is/are correct ?
- 1. It was launched by the Ministry of Ports, Shipping and Waterways, Government of India.
- 2. Matsya-6000 has been designed to carry 3 people for deep sea exploration.
- 3. Samudrayaan is a project under this mission.
Select the answer using the code given below :
Answer (b) & explanation
Statements 2 and 3 are correct (b). Statement 2 is right: Matsya-6000 is a submersible designed to take three people to a depth of 6,000 metres. Statement 3 is right: Samudrayaan is the project under the mission that is building it. Statement 1 is wrong: the Deep Ocean Mission (2021) belongs to the Ministry of Earth Sciences, not the shipping ministry. So options (a), (c) and (d) fail.
Notice the mission's other parts: deep-sea mining of polymetallic nodules in the Central Indian Ocean Basin, ocean biodiversity, and climate advisory services. The National Institute of Ocean Technology in Chennai builds Matsya. Only a few countries, such as the USA, China, Japan and France, have crewed deep-sea vehicles.
Answer as per the official UPSC answer key.
Consider the following space missions :
- I. Axiom-4
- II. SpaDeX
- III. Gaganyaan
How many of the space missions given above encourage and support micro-gravity research?
Answer (b) & explanation
Two of the missions support microgravity research (b). Item I is right: Axiom-4 (2025) took Shubhanshu Shukla to the International Space Station, where he ran Indian microgravity experiments, such as on sprouting seeds and muscle loss. Item III is right: Gaganyaan is designed to carry microgravity experiments on its crewed and uncrewed flights. Item II is not counted in UPSC's key: SpaDeX was a docking technology demonstration, though it did carry some small payloads.
Notice SpaDeX's importance: in January 2025 India became the fourth country to dock two satellites in space, after the USA, Russia and China. Docking is needed for the planned Bharatiya Antariksh Station and the Chandrayaan-4 sample return.
Answer as per the official UPSC answer key.
Consider the following pairs :
| Plant | Description
| I. Cassava | Woody shrub
| II. Ginger | Herb with pseudostem
| III. Malabar spinach | Herbaceous climber
| IV. Mint | Annual shrub
| V. Papaya | Woody shrub
How many of the above pairs are correctly matched?
Answer (b) & explanation
Three pairs are correctly matched (b). Pair I is right: cassava is a woody shrub grown for its starchy roots. Pair II is right: ginger is a herb whose leafy "stem" is a pseudostem of rolled leaf sheaths above the rhizome. Pair III is right: Malabar spinach is a soft, herbaceous climber. Pair IV is wrong: mint is a perennial herb, not an annual shrub. Pair V is wrong: papaya is a soft-stemmed, tree-like plant, not a woody shrub.
Notice the term pseudostem: the banana plant also has one, which is why it is a giant herb, not a tree. Cassava, also called tapioca, is a major crop in Kerala and a staple food across Africa.
Answer as per the official UPSC answer key.
GPS-Aided Geo Augmented Navigation (GAGAN) uses a system of ground stations to provide necessary augmentation. Which of the following statements is/are correct in respect of GAGAN?
- I. It is designed to provide additional accuracy and integrity.
- II. It will allow more uniform and high quality air traffic management.
- III. It will provide benefits only in aviation but not in other modes of transportation.
Select the correct answer using the code given below.
Answer (d) & explanation
Statements I and II are correct (d). GAGAN, built by ISRO and the Airports Authority of India, corrects GPS signals using ground stations and geostationary satellites. Statement I is right: it adds accuracy and integrity. Statement II is right: it allows more uniform, high-quality air traffic management and safer aircraft approaches. Statement III is wrong: its signal is also used for railways, shipping, fishing alerts and surveying. So options (a), (b) and (c) fail.
Notice the difference: GAGAN improves GPS, while NavIC (IRNSS) is India's own independent regional navigation system. India was the third country, after the USA and Europe, with such an aviation-grade satellite-based augmentation system.
Answer as per the official UPSC answer key.
Consider the following types of vehicles :
- I. Full battery electric vehicles
- II. Hydrogen fuel cell vehicles
- III. Fuel cell-electric hybrid vehicles
How many of the above are considered as alternative powertrain vehicles?
Answer (c) & explanation
All three are alternative powertrain vehicles (c). An alternative powertrain is any drive system other than the conventional petrol or diesel engine. Item I is right: full battery electric vehicles run only on a battery and motor. Item II is right: hydrogen fuel cell vehicles make electricity from hydrogen. Item III is right: fuel cell–electric hybrid vehicles combine a fuel cell with a battery. So options (a), (b) and (d) fail. CNG and petrol-electric hybrid cars also count.
Notice India's push: the PM E-DRIVE scheme (2024) for electric vehicles, FAME before it, and the National Green Hydrogen Mission (2023). Flex-fuel cars running on ethanol blends are another option, with E20 petrol now sold across India.
Answer as per the official UPSC answer key.
With reference to Unmanned Aerial Vehicles (UAVs), consider the following statements :
- I. All types of UAVs can do vertical landing.
- II. All types of UAVs can do automated hovering.
- III. All types of UAVs can use battery only as a source of power supply.
How many of the statements given above are correct?
Answer (d) & explanation
None of the statements is correct (d). Each statement says "all types", which is the trap. Statement I is wrong: multi-rotor drones land vertically, but fixed-wing UAVs, such as most military drones, need a runway or a net. Statement II is wrong: fixed-wing UAVs cannot hover; they must keep moving forward. Statement III is wrong: large UAVs run on fuel engines, and some use solar power or hydrogen. So options (a), (b) and (c) fail.
Notice India's drone push: the Drone Rules, 2021, the PLI scheme for drones, and Namo Drone Didi, giving drones to women's self-help groups for spraying crops. India is buying US MQ-9B drones, and drones were widely used in Operation Sindoor (2025).
"All types" in every statement is the clue. One counter-example, the fixed-wing drone, breaks all three.
Answer as per the official UPSC answer key.
In the context of electric vehicle batteries, consider the following elements :
- I. Cobalt
- II. Graphite
- III. Lithium
- IV. Nickel
How many of the above usually make up battery cathodes?
Answer (c) & explanation
Three of the four usually make up cathodes (c). A lithium-ion cathode is a lithium metal oxide, such as nickel-manganese-cobalt (NMC), nickel-cobalt-aluminium (NCA), or lithium iron phosphate (LFP). So lithium (III), nickel (IV) and cobalt (I) go into cathodes. Item II is wrong: graphite is the usual anode material, not the cathode. So options (a), (b) and (d) fail.
Notice the shift to LFP batteries, which avoid costly cobalt and are safer, now common in EVs. Sodium-ion batteries are an emerging cheaper option. India's PLI scheme for Advanced Chemistry Cell batteries aims to make cells at home, and the Kolar and Jammu lithium finds made news.
Answer as per the official UPSC answer key.
Consider the following substances :
- I. Ethanol
- II. Nitroglycerine
- III. Urea
Coal gasification technology can be used in the production of how many of them?
Answer (b) & explanation
Coal gasification can produce two of them (b). Gasification turns coal into syngas, a mix of carbon monoxide and hydrogen. Item III is right: syngas can be made into ammonia and then urea, as at the revived Talcher fertiliser plant. Item I is right: syngas can be made into methanol and ethanol, which is why India's coal gasification mission names these products. Item II is wrong: nitroglycerine is made by nitrating glycerol, which comes from fats, not from syngas.
Notice the National Coal Gasification Mission, aiming to gasify 100 million tonnes of coal by 2030, to cut imports of gas, ammonia and methanol. Gasification is cleaner than burning coal directly, but still emits CO₂.
Answer as per the official UPSC answer key.