Why Is There So Much Variation in Human Skin Coloration

Why is there so much variation in human skin coloration?

A) This occurred because humans underwent natural selection,which resulted in traits that conferred advantages to humans becoming fixed in populations.
B) This occurred because skin coloration results in different advantages depending on the levels of sun in the region.
C) This occurred because alleles that are harmful in one environmental context may be beneficial in another.
D) This occurred because humans are found in areas that range from high-UV-light environments to low-UV-light environments.
E) all of these