Refer to the Given Diagram, in Which Line AB Is

Refer to the given diagram, in which line AB is the U.S. production possibilities curve and AC is its trading possibilities curve. We can conclude that the United States

A) has chosen to specialize in the production of cheese.
B) has chosen to specialize in the production of beef.
C) has decided to trade beef for cheese.
D) is relatively more efficient than its trading partners in producing both cheese and beef.