Answer:
Geographic obstacle:hills,mud,rocks.
Political obstacle: Mexicans didn't want to give up land.
The answer is most likely A.
Melting pot theory
Hope this helps
The United States and the USSR were the lone remaining superpowers left after World War II.
As a result, they viewed proxy wars much like a chess player viewed moving a pawn. If they could get a strategic advantage in Algeria or El Salvador or Cuba, they would take it and lord it over the losing superpower.