Answer:
C. The belief that the United States was destined by God to settle territory as far as the Pacific Ocean.
Step-by-step explanation:
Wikipedia does a better job at explaining it than I do.
"Manifest destiny was a widely held cultural belief in the 19th-century United States that American settlers were destined to expand across North America. There are three basic themes to manifest destiny:
1. The special virtues of the American people and their institutions
2. The mission of the United States to redeem and remake the west in the image of the agrarian East
3. An irresistible destiny to accomplish this essential duty"