Answer:
A. The belief that the United States should extend from the Atlantic.
Step-by-step explanation:
Manifest Destiny can be defined as the long-held belief that the United States should extend from the Atlantic.
This ultimately implies that, the Manifest Destiny was a long-held belief around the 19th century, that the United States of America should expand from the Atlantic Ocean to the Pacific Ocean because the people felt it was justified and inevitable.