Jane and John are twins who attended grammar school through college together. Jane and John both got jobs at a brokerage firm after graduating from college with the same major. They both work equally hard. Jane earns $43,000 a year, and John earns $69,000 a year. Select the best explanation for this wage difference.

a. Jane has less human capital than John.
b. Jane has more human capital than John.
c. Jane has been discriminated against because she is female.
d. John has been discriminated against because he is male.