Assume That the Average Male Wage Rate Is 20% Higher

Assume that the average male wage rate is 20% higher than the average female wage rate. One can infer that:

A) this is evidence of discrimination because females should be paid the same as males.
B) employers undervalue female employees, so they're able to pay them less.
C) customers overvalue male employers, so employers pay males more.
D) this is evidence of discrimination only if all factors affecting productivity are equal.