Plsss help Worth a lot of points

15) To aid their trading with Native Americans.

16) Mississippi River and St. Lawrence River

17) Fort Maurepas

18) Spain. France regained it in 1803.

19) He sold it to the United States.

20) Detroit, New Orleans, Baton Rouge

Explanation:

answer is b.

  it is always the best policy to have good communication and good relations between individuals and, specially, between leaders of the countries. for this purpose, among others, there is a common place, the united nations, where the representants can present his and learn about the other country's policies.

the answer is a. physical map