Under which condition does river deposition become more prominent than erosion?

Correct answer: When slope and velocity decrease and sediment load starts settling

The direct answer is A: deposition becomes more prominent when slope and velocity decrease while the river still carries sediment. A river can carry particles only while its speed and energy are sufficient. On a steep mountain slope, water is usually fast and has strong erosive power. As the river reaches flatter land, its speed often falls because the gradient decreases. It then cannot carry all its sand, silt, and gravel, so the load settles on the bed or banks. Option A states this complete cause-and-effect chain. Option B is wrong because a steep mountain slope generally encourages erosion and transportation, not dominant deposition. Option C is wrong because without sediment there is nothing substantial to deposit. Option D is wrong because water locked as ice is not flowing river water in this situation. Flood plains, natural levees, meanders, and deltas are common examples of deposition. Exam cue: less slope plus less speed means settling.