UPSC Prelims 2020— Question 100

This question tests biochar. The key concept is: Biochar is a stable carbon-rich material that can be incorporated into growing media and soils. It can improve water-holding capacity and habitat conditions for beneficial microorganisms, including organisms involved in nutrient cycling. It is therefore useful in vertical-farming media as well as conventional soil systems. The verified answer for the uploaded Set-B paper is option D. Option A — 1 and 2 only: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: Biochar is a stable carbon-rich material that can be incorporated into growing media and soils. It can improve water-holding capacity and habitat conditions for beneficial microorganisms, including organisms involved in nutrient cycling. It is therefore useful in vertical-farming media as well as conventional soil systems. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option B — 2 only: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: Biochar is a stable carbon-rich material that can be incorporated into growing media and soils. It can improve water-holding capacity and habitat conditions for beneficial microorganisms, including organisms involved in nutrient cycling. It is therefore useful in vertical-farming media as well as conventional soil systems. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option C — 1 and 3 only: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: Biochar is a stable carbon-rich material that can be incorporated into growing media and soils. It can improve water-holding capacity and habitat conditions for beneficial microorganisms, including organisms involved in nutrient cycling. It is therefore useful in vertical-farming media as well as conventional soil systems. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option D — 1, 2 and 3: This is the correct option. It matches the verified conclusion because Biochar is a stable carbon-rich material that can be incorporated into growing media and soils. It can improve water-holding capacity and habitat conditions for beneficial microorganisms, including organisms involved in nutrient cycling. It is therefore useful in vertical-farming media as well as conventional soil systems. The wording of the option is consistent with the governing concept tested by the question. For UPSC-style elimination, first identify the exact proposition being tested, then evaluate each statement independently before comparing the answer codes. Avoid treating a broad or absolute statement as correct merely because its general theme is familiar. The precise qualifiers in the question—such as 'all', 'only', 'cannot', 'largest', 'always' or a specific institutional role—often determine the answer. On that basis, option D is the verified answer.