Regarding to the Empirical Research on Discrimination in Canada, Which

Regarding to the empirical research on discrimination in Canada, which of the following is correct?

A) The earning differentials between white and aboriginals have declined recently.
B) More Canadian research is focused on ethnic-white earning differentials.
C) Wage gaps of black workers with high school education are substantially reduced after controlling for differences in ability scores.
D) The research on ethnic-white earning differentials is difficult due to data limitations.
E) Earnings disadvantages for immigrants distribute evenly across the countries of origin of the immigrants.