Which statement summarizes the central idea of the article?

A) The Louisiana Purchase greatly changed the United States geographically and economically.
B) The Louisiana Purchase had very little impact on the culture and politics of the United States.
C) The Louisiana Purchase opened up trade along the Mississippi River for the first time in US history.
D) The Louisiana Purchase strengthened ties between the United States and both France and Spain.

A IS THE CORRECT ANSWER. I DIDN'T SEE THIS QUESTION ON HERE SO I FIGURED I'D HELP PEOPLE OUT.