How do waterfalls form?

A. meander gets cut off.

B. Sediment builds up.

C. Soft rock erodes.

D. Flat areas flood.

Soft rock erodes

Explanation:

Often, waterfalls form as streams flow from soft rock to hard rock. This happens both laterally (as a stream flows across the earth) and vertically (as the stream drops in a waterfall). In both cases, the soft rock erodes, leaving a hard ledge over which the stream falls.