Answer:
They ended up colonizing North America for different economic reasons. Spain colonized America because they were searching for gold and silver. They did find a lot of gold and silver when they conquered the Aztec and Inca Empires. France colonized North America because of the great amount of furs they found there.
D. Contain the spread of Communism in every region of the world
The domino theory said that if one country falls to Communism, then the nations it associates with will turn to Communism as well. So, the solution for this was try to contain Communism so it wouldn't spread.