UPSC Prelims 2014— Question 18

Correct answer: Option D. Engineered nanoparticles can create environmental concerns because their small size and high surface reactivity can allow persistence, movement through environmental media and biological uptake. They may enter food chains and, depending on the material, can generate reactive oxygen species or free radicals. Thus all three statements identify recognized concerns. Option A: Incorrect. This option does not match the verified answer because its proposition, location, institution, sequence, or combination conflicts with the relevant fact tested in the question. The option reads: “1 and 2 only” Option B: Incorrect. This option does not match the verified answer because its proposition, location, institution, sequence, or combination conflicts with the relevant fact tested in the question. The option reads: “3 only” Option C: Incorrect. This option does not match the verified answer because its proposition, location, institution, sequence, or combination conflicts with the relevant fact tested in the question. The option reads: “1 and 3 only” Option D: Correct. This option is consistent with the governing fact or the valid combination identified in the question. The option reads: “1, 2 and 3” The key Prelims lesson is to test each proposition independently before selecting the combination. Where the question uses words such as 'only', 'all', 'none', 'always' or a precise institutional/geographical association, a single inaccurate component is sufficient to eliminate the option. The answer recorded here follows the official answer key for the question-paper series represented by the uploaded source and has been cross-checked against an independent published key. The explanation is intended for conceptual revision rather than as a reproduction of any third-party solution.