Arrange the following countries in the descending order of their number of nuclear power plants and select the correct answer from the codes given below: 1) France 2) Japan 3) Russia 4) U.S.A.

The correct order by number of nuclear reactors is USA, France, Japan, Russia, which is option C (4, 1, 2, 3). In 2013 the USA had about 100 reactors, far ahead of the rest. France had about 58, built in a fast programme after the 1973 oil shock, and nuclear supplies roughly three-quarters of its electricity. Japan had about 50 reactors on paper, but after Fukushima in 2011 nearly all were offline for safety review, so its operating count was much lower than its fleet. Russia had about 33, the smallest of the four.

Option A puts Russia first, which is wrong because the USA and France both have more reactors. Option B puts France first and the USA third, which reverses the top two. Option D puts Russia second, ahead of Japan and France, which does not match the fleet sizes.

Core concept: nuclear power capacity and the reactor fleet of major producers. It links to the energy security and climate change themes in GS-III, and to Mains questions on why France relies on nuclear power while Germany chose to phase it out.

Trap: candidates either recall Japan's reactor count without considering the post-Fukushima shutdowns, or confuse the number of reactors with installed capacity in GW. Check which metric the question asks for.