How did the mexican-american war lead to the civil war?

the war was the westward expansion of the United States. All through the 19th century Americans believed it was their right to expand westward. At the time they believed they could conquer the people already living on the land and take it for the United States.

the correct labels are as follows:

a: yellow river

b: himalayan mountains

c: north china plain

d: taklimakan desert