The Two-Country General Equilibrium (PPF/indifference Curves) Model Illustrates That

The two-country general equilibrium (PPF/indifference curves) model illustrates that:

A) there are gains from trade whenever price ratios of goods are different across countries.
B) relative prices within economies will differ only when production possibilities frontiers differ.
C) differences in production possibilities frontiers may be due to differences in tastes.
D) All of the above.
E) None of the above.