What Does the Study of the Balance of International Trade

What does the study of the balance of international trade and finance between 1790 and 1860 help American economic historians do?

A) Understand what the U.S. sold to the rest of the world
B) Understand what the rest of the world sold to the U.S.
C) Determine if there is a link between these international patterns and ?economic growth in the U.S.
D) All of the above