C - He thought it would be easier than trying to conquer the territory.
A is incorrect as, at the time, the United States and France were allies and would not be going to war at any time during this time period.
B is incorrect as, well, how would this aid the French in a war with Britain? If France needed funds from an ally, they could do so.
D is incorrect as, well, the Louisiana Purchase had no access to the Caribbean or the sea much.
Hope this helps!
