Why is tree plantation along rivers useful?

Correct answer: It can reduce bank erosion

The direct answer is A, tree plantation can reduce bank erosion. River-bank erosion happens when flowing water removes soil from the sides of a river. Step by step: tree roots grow through the soil and bind soil particles; roots and vegetation slow some surface runoff; plant cover protects the exposed ground from rain and moving water; as a result, the bank may become more stable and less easily washed away. Option A is correct because it describes this erosion-control role. Option B, immediately drying the river, is not a function of planting trees. Option C, increasing plastic, is pollution and has no necessary connection with plantation. Option D, turning fish into stones, is impossible and unrelated. Trees cannot stop all erosion: floods, strong currents and poor planting choices may still damage banks, so the wording “can reduce” is accurate. Memory cue: roots grip the bank; plantation helps prevent soil loss.