Which of the Following BEST Describes the Evolutionary Basis for Variation

Which of the following BEST describes the evolutionary basis for variation in human skin color?

A) Skin color is lighter at high latitudes than it is toward the equator.UV radiation is weaker at high latitude,so we don't need to protect against the breakdown of folate.Lighter skin color permits enough UV to be absorbed to build vitamin D.
B) Skin color is lighter at high latitudes than it is toward the equator.UV radiation is weaker at high latitude,so we need light skin to allow the buildup of folate.UV radiation is too weak to break down vitamin D.
C) Skin color is darker near the equator.UV radiation is stronger there,so we need dark skin to protect us from folate breakdown.Enough UV radiation will still be absorbed to provide enough vitamin D.
D) Skin color is darker near the equator.UV radiation is stronger there,so we need dark skin to protect against vitamin D breakdown.Enough UV radiation will still be absorbed to provide enough folate.
E) A and C together make up the best explanation.