During a thunderstorm, the thunder in the skies is produced by the 1. meeting of cumulonimbus clouds in the sky 2. lightning that separates the nimbus clouds 3. violent upward movement of air and water particles Select the correct answer using the codes given below.

Thunder is a sound, and its source is the sudden heating of air by a lightning discharge. A lightning channel can reach temperatures near 30,000 K, so the surrounding air expands explosively and sends out a shock wave that we hear as thunder. Lightning is the cause of thunder, not a separate event, and that is where statement 2 goes wrong.

Statement 1 is wrong because clouds do not collide to produce thunder; cumulonimbus clouds are simply the storm clouds where charging happens. Statement 2 is wrong because lightning does not separate nimbus clouds; it is a discharge of electric charge built up inside or between clouds and between cloud and ground. Statement 3 describes a process inside the cloud: violent updraughts and collisions of ice and water particles separate positive and negative charge, which sets up lightning. It is a precursor, not the direct source of the sound.

So none of the three statements correctly identifies the origin of thunder, and the answer is D.

Core concept: thunder is the acoustic consequence of rapid thermal expansion of air along the lightning channel. It links to the physical geography and disaster management units, and to Mains questions on lightning as a hazard and on early warning systems.

Trap: candidates pick statement 3 because it sounds like a storm mechanism. Statement 3 explains charge separation, not the sound.