Science & Technology MCQs for UPSC Prelims

Q1. With reference to pumped storage projects (PSPs) and battery energy storage systems (BESS) in India's power system, consider the following statements: Which of the statements given above are correct?

1. PSPs are suited to long-duration bulk storage, whereas BESS is typically deployed for short-duration needs.
2. Reliance on imported battery cells is an energy-security concern for BESS that PSPs, built mainly with domestic civil works, largely avoid.
3. Because batteries respond faster, the CEA's projection of storage needs for 2031–32 relies on BESS alone.
4. PSPs can provide peaking support, reducing reliance on fossil-fuel plants to meet peak demand.

• A. 1, 2 and 4 only
• B. 1, 3 and 4 only
• C. 2, 3 and 4 only
• D. 1 and 2 only

Q2. Consider the following statements: Which of the following is correct in respect of the above statements?

1. Pumped storage plants are preferably sited where two reservoirs can be built with a large difference in elevation between them.
2. Pumped storage plants are especially valuable in grids with a high share of variable solar and wind generation.

• A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
• B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
• C. Statement-I is correct, but Statement-II is incorrect
• D. Statement-I is incorrect, but Statement-II is correct

Q3. With reference to the working of a pumped storage hydropower plant, consider the following statements: Which of the statements given above is/are correct?

1. Because the same water is recycled between its two reservoirs, a pumped storage plant is a net producer of electricity over a full pumping-and-generating cycle.
2. A single reversible machine can work as a pump when rotated in one direction and as a turbine when rotated in the other.
3. Its value to the grid lies mainly in shifting energy from periods of surplus or low demand to periods of peak demand.

• A. 1 and 3 only
• B. 1 and 2 only
• C. 2 and 3 only
• D. 1, 2 and 3

Q4. With reference to pumped storage projects (PSPs) and battery energy storage systems (BESS) in India's power system, consider the following statements: Which of the statements given above are correct?

1. PSPs are suited to long-duration bulk storage, whereas BESS is typically deployed for short-duration needs.
2. Reliance on imported battery cells is an energy-security concern for BESS that PSPs, built mainly with domestic civil works, largely avoid.
3. Because batteries respond faster, the CEA's projection of storage needs for 2031–32 relies on BESS alone.
4. PSPs can provide peaking support, reducing reliance on fossil-fuel plants to meet peak demand.

• A. 1, 2 and 4 only
• B. 1, 3 and 4 only
• C. 2, 3 and 4 only
• D. 1 and 2 only

Q5. Consider the following statements: Which of the following is correct in respect of the above statements?

1. Pumped storage plants are preferably sited where two reservoirs can be built with a large difference in elevation between them.
2. Pumped storage plants are especially valuable in grids with a high share of variable solar and wind generation.

• A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
• B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
• C. Statement-I is correct, but Statement-II is incorrect
• D. Statement-I is incorrect, but Statement-II is correct

Q6. With reference to the working of a pumped storage hydropower plant, consider the following statements: Which of the statements given above is/are correct?

1. Because the same water is recycled between its two reservoirs, a pumped storage plant is a net producer of electricity over a full pumping-and-generating cycle.
2. A single reversible machine can work as a pump when rotated in one direction and as a turbine when rotated in the other.
3. Its value to the grid lies mainly in shifting energy from periods of surplus or low demand to periods of peak demand.

• A. 1 and 3 only
• B. 1 and 2 only
• C. 2 and 3 only
• D. 1, 2 and 3

Q7. Under the 'One Nation, One Time' initiative, Indian Standard Time (IST) is being disseminated from national timescales through Legal Metrology laboratories, with the participation of CSIR-NPL and ISRO. Consider the following statements about the likely consequences: Which of the statements given above is/are correct?

1. It reduces the exposure of networks such as telecom, power and banking to disruption or spoofing of foreign satellite navigation signals.
2. It removes the need for any ground-based atomic timescale, since NavIC satellites can keep IST independently of a ground reference.
3. It allows time stamps used in commercial and financial transactions to be traced to a national standard.

• A. 1 and 2 only
• B. 1 and 3 only
• C. 2 and 3 only
• D. 1 only

Q8. Consider the following statements: Which of the following is correct in respect of the above statements?

1. World Metrology Day is coordinated jointly by the International Bureau of Weights and Measures (BIPM) and the International Organization of Legal Metrology (OIML).
2. The OIML was established under the Metre Convention of 1875, the signing of which World Metrology Day commemorates.

• A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
• B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
• C. Statement-I is correct, but Statement-II is incorrect
• D. Statement-I is incorrect, but Statement-II is correct

Q9. In the context of India hosting the 61st meeting of the International Committee of Legal Metrology (CIML), consider the following statements: Which of the statements given above is/are correct?

1. Scientific metrology is concerned with realising and maintaining units of measurement, whereas legal metrology is concerned with regulatory requirements for measurements and measuring instruments.
2. The International Committee for Weights and Measures (CIPM) is the principal governing committee of the International Organization of Legal Metrology (OIML).
3. Decisions and recommendations adopted by the CIML automatically become binding law in every OIML Member State, with no national legislation needed.

• A. 1 only
• B. 1, 2 and 3
• C. 2 and 3 only
• D. 1 and 2 only

Q10. Consider the following facts: Radio telescopes in Australia recorded emissions from the Starlink, OneWeb and China's Guowang constellations, which are operated from different countries, and part of the radiation came from onboard electronics rather than from the satellites' transmitters. Which of the following inferences can be drawn from the above?

1. Effective control of such interference requires coordination among the several countries under whose authority these satellites operate.
2. Australia could end the interference at its telescopes by refusing to license these broadband services within its territory.
3. Satellites can affect observatories in countries other than those from which the satellites are operated.

• A. 1 and 2 only
• B. 1, 2 and 3
• C. 1 and 3 only
• D. 2 and 3 only

Q11. Consider the following facts: Radio telescopes at sites in rural Australia, far from large towns, recorded radio emissions from low-earth-orbit communication satellites over roughly 376 hours of observation, and some of these signals were about 100 billion times brighter than typical astronomical sources. Which of the following inferences can be drawn from the above?

1. Satellite interference is a problem only for observatories located in the Southern Hemisphere.
2. Siting a radio telescope far from towns and mobile towers does not, by itself, protect it from transmitters in orbit.
3. Within the affected frequencies, such signals can mask the faint emissions from cosmic sources.

• A. 1 and 2 only
• B. 2 and 3 only
• C. 1 and 3 only
• D. 1, 2 and 3

Q12. With reference to direct-to-cell satellite communication, consider the following statements: Which of the statements given above is/are correct?

1. Direct-to-cell service requires each user to install a dedicated satellite dish or terminal at the premises.
2. Being deliberate, licensed transmissions, direct-to-cell signals are classed as intended emissions in studies of satellite interference.
3. Because direct-to-cell signals are licensed, the transmitters producing them cannot give rise to emissions outside their assigned frequencies.

• A. 1, 2 and 3
• B. 1 only
• C. 2 and 3 only
• D. 2 only

Q13. With reference to communication satellites in low-earth orbit (LEO), consider the following statements: Which of the statements given above is/are correct?

1. A single LEO satellite can see only a small part of Earth's surface at any one time, so continuous global service needs a very large number of satellites.
2. Because a LEO satellite is far closer to Earth than a geostationary satellite, signals to and from it have a shorter round-trip delay.
3. A LEO constellation meant to serve one country must still have its satellites pass over other parts of the world, as each satellite circles Earth's centre.

• A. 2 and 3 only
• B. 1, 2 and 3
• C. 1 and 3 only
• D. 1 and 2 only

Q14. Consider the following statements: Which of the following is correct in respect of the above statements?

1. Emissions from communication satellites in low-earth orbit can threaten radio observations of hydroxyl molecules in space.
2. Hydroxyl molecules occur only in Earth's upper atmosphere, through which satellite signals pass on their way to the ground.

• A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
• B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
• C. Statement-I is correct, but Statement-II is incorrect
• D. Statement-I is incorrect, but Statement-II is correct

Q15. Consider the following assertion: A satellite emission at about 1,613 MHz can seriously hamper the study of hydroxyl molecules in space even if every other frequency remains free of interference. Which of the following statements support/supports the above assertion?

1. Molecules such as hydroxyl emit radio waves at their own characteristic frequencies, so studying them depends on those particular frequencies.
2. Natural radio emissions from distant cosmic sources are extremely faint by the time they reach Earth, so a man-made signal at the same frequency can drown them out.
3. Radio telescopes can observe hydroxyl only at night, when satellites are hidden in Earth's shadow.
4. Satellite signals received at ground level are generally weaker than typical astronomical sources.

• A. 2 and 3 only
• B. 1, 2, 3 and 4
• C. 1 and 2 only
• D. 1, 3 and 4 only

Q16. Consider the following statements: Which of the following is correct in respect of the above statements?

1. Restricting only the frequencies and power at which satellites are licensed to transmit cannot by itself remove all the radio interference they cause to radio telescopes.
2. Onboard components of satellites, such as power converters and computers, give off stray electromagnetic radiation that does not come from the satellite's licensed transmission chain.

• A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
• B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
• C. Statement-I is correct, but Statement-II is incorrect
• D. Statement-I is incorrect, but Statement-II is correct

Q17. With reference to the classification of radio emissions from communication satellites used in recent radio-astronomy studies, consider the following statements: Which of the statements given above is/are correct?

1. Electromagnetic noise from a satellite's power converters counts as an unwanted emission, because the equipment producing it supports the satellite's transmitter.
2. Signals that a satellite's transmitter leaks outside its assigned frequency band count as unwanted emissions.
3. Unintended radiation can be emitted even at times when a satellite's transmitter is not radiating.

• A. 2 and 3 only
• B. 1 and 3 only
• C. 1, 2 and 3
• D. 1 and 2 only

Q18. With reference to radiocarbon dating as used at early historic sites, consider the following statements: Which of the statements given above is/are correct?

1. The fraction of carbon-14 remaining shrinks with age, which is why the method stops being useful beyond roughly 50,000 years.
2. After an organism dies, its carbon-14 keeps being replenished from the atmosphere, so the amount in it stays constant.
3. A raw radiocarbon age has to be calibrated before it can be read as a calendar date.
4. A sample about 2,000 years old would retain less than half of its original carbon-14.

• A. 1 and 3 only
• B. 2 and 4 only
• C. 1, 2, 3 and 4
• D. 1, 3 and 4 only

Q19. Consider the following statements: Which of the following is correct in respect of the above statements?

1. India's AI Governance Guidelines avoid making mandatory approvals or licensing a general precondition for AI deployment, unless it is necessary.
2. Under the IndiaAI Mission, tens of thousands of GPUs have been onboarded and offered to users at subsidised rates.

• A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
• B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
• C. Statement-I is correct, but Statement-II is incorrect
• D. Statement-I is incorrect, but Statement-II is correct

Q20. With reference to risk-based regulation of artificial intelligence, consider the following statements: Which of the statements given above is/are correct?

1. Under the European Union's AI Act, AI systems classified as high-risk are barred from being placed on the EU market.
2. Under a risk-based model, the same underlying AI technique may face different obligations depending on the purpose for which it is deployed.
3. A power to block an AI model only when its expected harm crosses a catastrophic threshold follows the risk-based logic of reserving the strongest controls for the gravest risks.

• A. 1 and 3 only
• B. 1, 2 and 3
• C. 2 and 3 only
• D. 1 and 2 only

Q21. Consider the following statements: Which of the following is correct in respect of the above statements?

1. Replacing furnace oil with natural gas in an industrial furnace sharply reduces its sulphur dioxide emissions.
2. Sulphur compounds present in raw natural gas are largely removed during processing, leaving only trace amounts in the gas that is supplied.

• A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
• B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
• C. Statement-I is correct, but Statement-II is incorrect
• D. Statement-I is incorrect, but Statement-II is correct

Q22. Suppose a drinking-water standard caps chromium at 0.05 mg/L, measured as total chromium (trivalent plus hexavalent), and only the hexavalent form is of serious health concern. Consider the following inferences: Which of the inferences given above is/are valid?

1. Water that meets this standard cannot contain more than 0.05 mg/L of hexavalent chromium.
2. Water that fails this standard must contain more than 0.05 mg/L of hexavalent chromium.
3. Water can fail this standard even when its hexavalent chromium content alone is below 0.05 mg/L.

• A. 1 and 3 only
• B. 1, 2 and 3
• C. 1 only
• D. 2 and 3 only

Q23. Authorities plan to inject a chemical reducing agent into an aquifer contaminated with hexavalent chromium. If the treatment works as intended, which one of the following is the most likely outcome?

• A. Chromium changes into a more soluble form that flowing groundwater flushes out of the aquifer faster.
• B. Chromium changes into a volatile form that escapes from the groundwater into the atmosphere above.
• C. Chromium changes into a less toxic form that tends to settle out of water and bind to the soil.
• D. Chromium is broken down by the reagent into carbon dioxide, water and other harmless mineral salts.

Q24. With reference to chromium in drinking water, consider the following statements: Which of the statements given above is/are correct?

1. Because trivalent chromium is regarded as a trace nutrient, the toxicity of chromium in drinking water does not depend on its oxidation state.
2. A measurement of total chromium in water counts both the trivalent and the hexavalent forms, although the health hazard arises mainly from the hexavalent form.

• A. 1 only
• B. 2 only
• C. Both 1 and 2
• D. Neither 1 nor 2

Q25. Consider the following statements: Which of the following is correct in respect of the above statements?

1. Chromium leaching from dumps of chrome-tanning waste is far more likely to travel through aquifers to distant wells when it is in the hexavalent state than when it is in the trivalent state.
2. Hexavalent chromium compounds are soluble and mobile in soil and water, whereas trivalent chromium tends to precipitate and bind strongly to mineral and organic surfaces.

• A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
• B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
• C. Statement-I is correct, but Statement-II is incorrect
• D. Statement-I is incorrect, but Statement-II is correct

Q26. A shipyard moves from conventional construction to extensive modular construction with pre-outfitting. Consider the following likely consequences: Which of the above are correct?

1. Harbour and sea trials of the completed ship are no longer required.
2. A larger share of pipe, cable and equipment fitting is done on separate blocks rather than inside the confined, completed hull.
3. Precise dimensional control becomes more important, because blocks fitted out separately must line up when they are joined.
4. Design changes made late in construction become easier and cheaper to absorb.

• A. 1 and 4 only
• B. 1, 2 and 3 only
• C. 2 and 3 only
• D. 3 and 4 only

Q27. Compared with surveillance based on clinical isolates collected from hospitals, wastewater-based surveillance of antimicrobial resistance is distinctive mainly because it

• A. yields patient-level resistance profiles that guide individual antibiotic choices
• B. measures resistance among hospital patients but not in the wider community
• C. captures resistance carried by people who never seek care or get tested
• D. detects resistance only after hospitals report a rise in treatment failures

Q28. Consider the following assertion: Tracking antimicrobial resistance effectively requires surveillance across the human–animal–environment interface rather than in hospitals alone. Which of the following statements support/supports the above assertion?

1. Misuse and overuse of antimicrobials in animals and plants, and not only in humans, drive the development of drug-resistant pathogens.
2. The WHO Global Action Plan on antimicrobial resistance has been updated to cover the period 2026–2036.
3. Resistant microbes and antimicrobial residues enter the environment through effluents and sewage.

• A. 1, 2 and 3
• B. 1 and 3 only
• C. 1 and 2 only
• D. 2 and 3 only

Q29. With reference to biosafety levels (BSL) for laboratories, consider the following statements: Which of the statements given above is/are correct?

1. Biosafety levels are graded by the risk posed by the agents handled, with BSL-3 designated as 'containment' and BSL-4 as 'maximum containment'.
2. BSL-3 is the highest containment grade, so work on agents for which no effective treatment or vaccine exists is carried out in BSL-3 facilities.
3. Agents requiring the highest containment usually cause serious disease and can be readily transmitted from one individual to another.

• A. 1 and 3 only
• B. 1, 2 and 3
• C. 2 and 3 only
• D. 1 and 2 only

Q30. A 2026 Lancet Commission listed 17 interlinked catastrophic threats to global health through 2100, among them pandemics, antimicrobial resistance, obesity, air pollution, nuclear conflict and artificial intelligence. It urged leaders to stop treating these issues in isolation, while acknowledging that the past focus of global health activism on particular domains had produced many benefits. Which of the following inferences can be drawn from the above?

1. The Commission regards threats to human health as capable of arising outside the biomedical domain.
2. The Commission holds that disease-specific global health programmes have, on balance, been counterproductive.
3. The Commission's framing implies that action taken on one threat may change the risks posed by others.
4. The Commission considers infectious diseases to be no longer among the principal threats to human health.

• A. 1, 2 and 3 only
• B. 1, 3 and 4 only
• C. 1 and 3 only
• D. 2 and 4 only