Why Do African Populations of Humans Have HIGHER Levels of Genetic

Why do African populations of humans have HIGHER levels of genetic variation compared with non-African populations?

A) Humans originated in Africa, and subsequent migrations resulted in populations seeded by small groups with relatively small amounts of variation.
B) Because African populations show strong patterns of nonrandom mating.
C) Numerous migrations to Africa throughout early human history have increased genetic diversity there.
D) High levels of UV radiation in equatorial regions of the world have increased levels of genetic mutations in Africa.