Which of the following statements is true?

a. Exports tend to decrease economic efficiency.
b. A nation should specialize in producing a good in which it has an absolute advantage.
c. A nation should specialize in producing a good only when it has both an absolute and a comparative advantage.
d. A nation should specialize in producing a good in which it has a comparative advantage.
e. International trade does not reflect the benefits of specialization.

D