Why did napoleon bonaparte give up on his hopes of building a north american empire?

-French North American mainland territory had been unproductive and costly to maintain in past wars, something that Napoleon knew he could not afford in the upcoming wars. 
-Britain had already declared war on France, surely part of the reason was to try and encourage better Franco-American relations. Surely Napoleon had some idea of American pride and stubbornness as well, once the U.S. controlled the territory

-Napoleon knew that there was no way any European power (Britain specifically) would conquer the territory. 

 Napoleon needed money and the sale of the Louisiana territory brought France some much needed capital.

i think the answer is c, rivers.

explanation:

sometimes, borders fall along natural boundaries like rivers or mountain ranges. for example, the boundary between france and spain follows the crest of the pyrenees mountains. for part of its length, the boundary between the united states and mexico follows a river called the rio grande. the borders of four countries divide africa’s lake chad: niger, chad, cameroon, and nigeria.

d.prevent the spread of communism outside of eastern europe.