If an Economist Develops a Theory About International Trade Based

If an economist develops a theory about international trade based on the assumption that there are only two countries and two goods:

A) the theory can be useful only in situations involving two countries and two goods
B) it is a total waste of time, since the actual world has many countries trading many goods
C) the theory can be useful in helping economists understand the complex world of international trade involving many countries and many goods
D) the theory can be useful in the classroom, but has no use in the real world