Explanation
- A
1 and 2 only
(a) 1 and 2 only. Abandoned coal seams and depleted hydrocarbon reservoirs are valid CO2 sinks, but deep saline formations are also standard sequestration geology. Omitting 3 is incomplete.
- B
3 only
(b) 3 only. Saline aquifers work, but they are not the only class. Not the key.
- C
1 and 3 only
(c) 1 and 3 only. Oil and gas reservoirs are a major enhanced-oil-recovery / storage option. Dropping 2 is wrong.
- D
1, 2 and 3
(d) 1, 2 and 3. Uneconomic coal seams, depleted oil and gas fields, and deep saline formations are all recognised geological stores for captured CO2. This is the official key.
Summary. Official key is (d) 1, 2 and 3. Geological carbon sequestration injects compressed CO2 into porous rock isolated by caprock. Unmineable coal can adsorb CO2; depleted oil and gas reservoirs have known seals and may yield extra hydrocarbons; deep saline formations offer the largest pore volume. Forests and soils are biological sinks, not asked here. All three listed sites count.
Same topic · past papers
UPSC has asked this before
These previous-year questions sit on the same topic. Open one to practise the earlier ask.
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