2017 GS Paper I, all questions

UPSC Prelims 2017 · GS Paper I

Question 25: Environment and Ecology

In the context of mitigating the impending global warming due to anthropogenic emissions of carbon dioxide, which of the following can be the potential sites for carbon sequestration ?

  1. 1.Abandoned and uneconomic coal seams
  2. 2.Depleted oil and gas reservoirs
  3. 3.Subterranean deep saline formations

Select the correct answer using the code given below :

a1 and 2 only
b3 only
c1 and 3 only
d1, 2 and 3

AnswerUPSC’s answer is (d).

Carbon dioxide can be injected into deep geological formations to keep it out of the atmosphere. Suitable sites include abandoned or uneconomic coal seams, depleted oil and gas reservoirs, and deep saline formations underground. All three listed are recognised sequestration sites. CO2 injected into oil fields can also push out remaining oil, which makes depleted reservoirs attractive. Remember: depleted oil and gas fields, unmineable coal seams and deep saline aquifers are the three main geological sinks.

  • 1. CO2 can be stored in unmineable or abandoned coal seams.
  • 2. Depleted oil and gas reservoirs are suitable storage sites.
  • 3. Deep saline formations can hold large volumes of CO2.

How you could have got this

  1. If you were sure statement 2 is correct, (b) and (c) go: each of them leaves 2 out.

    What you needed to know: Depleted oil and gas reservoirs are suitable storage sites.

  2. Then, if you were sure statement 3 is correct, (a) goes: it leaves 3 out.

    What you needed to know: Deep saline formations can hold large volumes of CO2.

Only (d) is left. You didn’t need statement 1.

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) Incomplete: saline formations (3) are also sites.
  • (b) Incomplete: coal seams and depleted reservoirs also qualify.
  • (c) Incomplete: depleted oil and gas reservoirs (2) also qualify.
  • (d) Right: all three are potential sequestration sites.

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

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Source: UPSC, Civil Services (Preliminary) Examination 2017, General Studies Paper I, Series A. The paper on upsc.gov.in.