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.

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.

a physical change is being made.