2023 GS Paper I, all questions

UPSC Prelims 2023 · GS Paper I

Question 20: Environment and Ecology

Consider the following :

  1. 1.Aerosols
  2. 2.Foam agents
  3. 3.Fire retardants
  4. 4.Lubricants

In the making of how many of the above are hydrofluorocarbons used?

aOnly one
bOnly two
cOnly three
dAll four

AnswerUPSC’s answer is (c).

Hydrofluorocarbons are used as propellants in aerosols, as blowing agents in making foams, and in fire suppression and fire-retardant systems, besides refrigeration and air conditioning. They are not used as lubricants, which are mineral or synthetic oils. HFCs replaced ozone-depleting CFCs and HCFCs but are potent greenhouse gases, so they are being phased down under the Kigali Amendment to the Montreal Protocol.

  • 1. HFCs serve as aerosol propellants.
  • 2. HFCs serve as foam blowing agents.
  • 3. HFCs are used in fire suppression and retardants.
  • 4. Lubricants are oil-based, not HFC-based.

How you could have got this

No shortcut here: in a “how many” question, ruling out options doesn’t help. Every statement has to be judged.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong
  • (a) Only one undercounts: aerosols, foams and fire retardants all use HFCs.
  • (b) Only two undercounts the uses of HFCs.
  • (c) Correct: aerosols, foam agents and fire retardants use HFCs; lubricants do not.
  • (d) Lubricants do not use HFCs, so not all four.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2023, General Studies Paper I, Series A. The paper on upsc.gov.in.