Why do mountain streams not meander and maintain the same course?

Question

A) The water moves very fast, keeping it on a straight path.
B) The mountain areas are cold, freezing the surface of the streams and preventing them from eroding the banks.
C) Mountain streams have huge boulders in them that prevent the erosion of the stream floor.
D) Mountain streams are lined with rock walls that prevent stream bank erosion.

Answer 1

C) Mountain streams have huge boulders in them that prevent the erosion of the stream floor.