The United States benefited from the Louisiana Purchase in the following ways:
A. It supplied the country with more natural resources.
B. It provided the country with access to a port for trading.
C. It doubled the size of the country.
So the correct answers are A, B, and C.
D is incorrect because Florida and Puerto Rico were not part of the Louisiana Purchase, and E is misleading because the expansion mainly involved territory west of the Mississippi River.