UPSC Prelims 2011— Question 35

Concept and answer: Option B is correct. Lower-stratospheric air is relatively stable and has weak vertical turbulence, making it favorable for smooth jet flight. The question should be approached by identifying the exact proposition being tested and then checking each alternative against that proposition. A familiar word or related fact is not enough; the option must be completely consistent with the underlying concept. Statement 1 is incorrect under the verified interpretation. Statement 2 is correct under the verified interpretation. Option A: Incorrect. It omits true statement(s) 2; includes false statement(s) 1. Option B: Correct. It selects exactly the valid statement combination and therefore matches the factual and logical requirements of the question. Option C: Incorrect. It includes false statement(s) 1. Option D: Incorrect. It includes false statement(s) 1. Exam takeaway: the decisive distinction is the one stated in the core explanation. Option B is the only choice that remains fully consistent with that distinction. This approach is useful for Prelims because many distractors contain a partially true statement but add an incorrect qualifier, reverse a relationship, confuse two institutions, or use an absolute term. Always test the entire option rather than recognizing only one familiar phrase.