UPSC Prelims 2021— Question 90

Lichens can colonize exposed surfaces without soil because they do not require a developed soil substrate and can grow directly on rock and other surfaces. Mosses can also establish on bare substrates, including rock, although their persistence often becomes associated with developing soil or organic matter. Ferns and mushrooms generally require more developed substrates. The accepted answer is 2 and 3. The final answer-key position for Set C identifies option C as the correct option. Option A — 1 and 4 only — is not correct because it does not satisfy the specific condition tested in the question; it represents an alternative that is contradicted, incomplete, or less precise than the accepted answer. Option B — 2 only — is not correct because it does not satisfy the specific condition tested in the question; it represents an alternative that is contradicted, incomplete, or less precise than the accepted answer. Option C — 2 and 3 — is correct because it is the alternative that matches the constitutional, historical, geographical, scientific or economic principle established above. Option D — 1, 3 and 4 — is not correct because it does not satisfy the specific condition tested in the question; it represents an alternative that is contradicted, incomplete, or less precise than the accepted answer. For PYQ interpretation, the distinction between the correct alternative and merely related facts is important. UPSC often places plausible distractors beside the precise statement that matches the underlying rule, chronology, definition or empirical relationship. The answer should therefore be read against the exact wording of the question rather than against a broadly related fact.