UPSC 2025 Science & Technology Previous Year Questions

Question 1

Artificial way of causing rainfall to reduce air pollution makes use of?

Accepted Answer

Correct Option: A. silver iodide and potassium iodide | silver nitrate and potassium iodide | silver iodide and potassium nitrate | silver nitrate and potassium chloride. Cloud seeding commonly uses silver iodide and potassium iodide to induce rainfall.

Question 2

With reference to India's defence, consider the following pairs: I. Dornier-228 : Maritime patrol aircraft II. IL-76 : Supersonic combat aircraft III. C-17 Globemaster III : Military transport aircraft How many of the pairs given above are correctly matched?

Accepted Answer

Correct Option: B. Only one | Only two | All the three | None. Dornier-228 is used for maritime patrol and C-17 is a military transport aircraft. IL-76 is a transport aircraft, not a supersonic combat aircraft.

Question 3

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?

Accepted Answer

Correct Option: B. Only one | Only two | All the three | None. Axiom-4 (a private astronaut mission to the ISS) and SpaDeX (whose POEM-4 module hosted microgravity experiments) encourage and support microgravity research; as per the official key, Gaganyaan is not counted. Hence two of the missions are counted.

Question 4

Consider the following statements: I. Indian Railways have prepared a National Rail Plan (NRP) to create a 'future ready' railway system by 2028. II. 'Kavach' is an Automatic Train Protection system developed in collaboration with Germany. III. 'Kavach' system consists of RFID tags fitted on track in station section. Which of the statements given above are not correct?

Accepted Answer

Correct Option: A. I and II only | II and III only | I and III only | I, II and III. The National Rail Plan target is not 2028 and Kavach is indigenously developed, not developed with Germany. RFID tags are part of Kavach, so statements I and II are not correct.

Question 5

Consider the following statements: Statement I: Some rare earth elements are used in the manufacture of flat television screens and computer monitors. Statement II: Some rare earth elements have phosphorescent properties. Which one of the following is correct in respect of the above statements?

Accepted Answer

Correct Option: A. Both Statement I and Statement II are correct and Statement II explains Statement I | Both Statement I and Statement II are correct but Statement II does not explain Statement I | Statement I is correct but Statement II is not correct | Statement I is not correct but Statement II is correct. Rare earth elements are used in display screens/monitors because some have phosphorescent/luminescent properties. Statement II explains Statement I.

Question 6

Consider the following statements: Statement I: Activated carbon is a good and an attractive tool to remove pollutants from effluent streams and to remediate contaminants from various industries. Statement II: Activated carbon exhibits a large surface area and a strong potential for adsorbing heavy metals. Statement III: Activated carbon can be easily synthesized from environmental wastes with high carbon content. Which one of the following is correct in respect of the above statements?

Accepted Answer

Correct Option: A. Both Statement II and Statement III are correct and both of them explain Statement I | Both Statement II and Statement III are correct but only one of them explains Statement I | Only one of the Statements II and III is correct and that explains Statement I | Neither Statement II nor Statement III is correct. Activated carbon's high surface area and adsorption capacity, and its production from carbon-rich wastes, explain its use in effluent treatment and remediation.

Question 7

Consider the following statements: I. No virus can survive in ocean waters. II. No virus can infect bacteria. III. No virus can change the cellular transcriptional activity in host cells. How many of the statements given above are correct?

Accepted Answer

Correct Option: D. Only one | Only two | All the three | None. Viruses can survive in ocean waters, bacteriophages infect bacteria, and viruses can alter host-cell transcription. None of the negative statements is correct.

Question 8

With reference to monoclonal antibodies, often mentioned in news, consider the following statements I. They are man-made proteins. II. They stimulate immunological function due to their ability to bind to specific antigens. III. They are used in treating viral infections like that of Nipah virus. Which of the statements given above are correct?

Accepted Answer

Correct Option: D. I and II only | II and III only | I and III only | I, II and III. Monoclonal antibodies are engineered/man-made proteins that bind specific antigens and can be used for viral infections, including experimental/therapeutic use for Nipah-like diseases. All three are correct.

Question 9

Consider the following statements I. It is expected that Majorana chip will enable quantum computing. II. Majorana 1 chip has been introduced by Amazon Web Services (AWS). III. Deep learning is a subset of machine learning. Which of the statements given above are correct?

Accepted Answer

Correct Option: C. I and II only | II and III only | I and III only | I, II and III. Majorana chips are expected to support quantum computing, and deep learning is a subset of machine learning. Majorana 1 was introduced by Microsoft, not AWS.

Question 10

What is the common characteristic of the chemical substances generally known as CL-20, HMX and LLM-105, which are sometimes talked about in media?

Accepted Answer

Correct Option: B. These are alternatives to hydrofluorocarbon refrigerants | These are explosives in military weapons | These are high-energy fuels for cruise missiles | These are fuels for rocket propulsion. CL-20, HMX and LLM-105 are high-energy explosive materials used in military weapons.

UPSC 2025 Science & Technology PYQs with Answers