Variance in reproductive success is a key driving factor in evolution. How does this affect sexual selection in mammals?

A) Male variance can be much greater than female variance, so males are potentially under very strong sexual selection.
B) Female variance can be much greater than female variance, so females are potentially under very strong sexual selection.
C) The level of variance determines the amount of resources shunted into parental investment; the sex with the highest variance produces the most food for offspring.
D) The sex with the lowest variance, usually mammals, has the highest average number of offspring.