What Accounts for the Fact That Polydactylism Is Prevalent and Tay-Sachs

Multiple Choice

What accounts for the fact that polydactylism is prevalent and Tay-Sachs disease is virtually absent in one human population in the United States, while Tay-Sachs disease is prevalent and polydactylism is virtually absent in another?

A) Natural selection has promoted these differences since humans live in many different environments.
B) Mutation rates differ among different loci.
C) There is little gene flow between the two populations.
D) The populations are small, and therefore genetic drift is a major factor in the determination of allele frequencies.
E) The alleles are fixed in these populations.