In a relatively small iguana population the allelic frequency is tracked for three generations. Webbing is a recessive allele; no webbing is the dominant allele. During one very rainy spring and summer, a flood washes all the iguana without webbed feet out to sea. By the fall, and three generations later, you have the gene pool seen here. This is an example of

A) gene flow.

B) immigration.

C) genetic drift.

D) founder effect.