What are the results of the American Westward Movement?
选项：

A:

The United States expanded its borders to include more than three million square miles.

B:

The United States became one of the most powerful nations in the 18th century and 19th century.

C:

The United States became one of the most powerful nations in the 20th century.

D:

The American Westward Movement resulted in great suffering, destruction, and cultural loss for the Native Americans of North America. ---the genocide of Native Americans or so-called Indians.

E: The American Westward Movement intensified the conflicts between the North and South and raised the question of whether slavery would be permitted in the western territories.