Assume That Empirical Evidence Shows a Difference in Mean Earnings

Assume that empirical evidence shows a difference in mean earnings between two groups, say, majority and minority workers. What conclusion may be drawn?

A) The group with the lower earnings is being discriminated against.
B) The group with the lower earnings is less productive.
C) The group with the lower earnings has less human capital.
D) Any of the above statements could, either partially or entirely, explain this difference.