Manifest destiny was the belief that
a. the united states should own most or all of north america.
b. the united states should invade and capture all of mexico.
c. slavery should extend westward beyond the south.
d. native americans had a right to the land they lost.

The answer is letter A.  They believe that it was their destiny to expand their hold on most of or all of the American continent.  They truly believe it was their mission to reshape America in their customs and traditions.  During period, population among white Americans was now growing and to accommodate them, they now started to travel to other lands and establish settlements there. Manifest Destiny however has been the cause of many conflicts such the wars with Native American tribes and the Mexican-American War where they acquired vast territories from Mexico.