Why can deposition increase when a Himalayan river enters the plains?

Correct answer: Carrying capacity decreases as slope and velocity reduce

Direct answer: Option C is correct. A river transports sediment only when its velocity and energy are sufficient. Himalayan rivers have greater slope and speed in the mountains. On entering the plains, the slope becomes gentler. The river slows down, its carrying capacity falls, and heavier particles such as gravel, sand, and silt can no longer remain in transport. They settle and deposition increases. Option C states this complete cause-and-effect chain. Option A is wrong because river water does not become saline merely on entering the plains. Option B is wrong because the river continues downhill, not uphill. Option D is wrong because a glacier does not fall directly into the sea as the explanation for ordinary plain-course deposition. The useful sequence is: mountain slope high → speed high → transport strong; plain slope low → speed lower → deposition greater. Exam cue: when flow becomes slower, expect sediment to be laid down.