The nation of Wheatland forbids international trade. In Wheatland, you can buy 1 pound of corn for 3 pounds of fish. In other countries, you can buy 1 pound of corn for 2 pounds of fish. These facts indicate that 
A、Wheatland has a comparative advantage, relative to other countries, in producing corn.
B、other countries have a comparative advantage, relative to Wheatland, in producing fish
C、the price of fish in Wheatland exceeds the world price of fish
D、if Wheatland were to allow trade, it would import corn