Dimitry Earns $10 an Hour Working at Costco

Dimitry earns $10 an hour working at Costco. During the school term he works 20 hours a week. In the summer he works 50 hours a week even though his wage is still $10. The explanation is that

A) there has been a fall in the price of a complementary product or service.
B) the marginal opportunity cost of his time is higher during the summer.
C) he expects his wage will be higher in the future.
D) the marginal opportunity cost of his time is lower during the summer.
E) the marginal benefit of the wage is higher in the summer.