A small, fast moving river is in a V-shaped valley on the slope of a mountain. If you follow the river to where it passes through a plain, what will the river most likely look like compared with how it looked on the mountain?

A) much the same

B) deeper and faster

C) slower and wider

D) straighter

The answer is C. Fast moving water, due to steep slopes in the mountain form V-shaped valley because the erosive power of the water is projected vertically more than horizontally. This is the vice versa in plains where the water moves at slower speeds. The horizontal erosion power is dominant over vertical erosion hence the banks of the river are eroded more than the bed in the plains.