Which of the following represents the belief used to justify westward expansion of americas borders in the 1800s ?
a. monroe doctrine
b. manifest destiny
c. adams -onis treaty
d. missouri compromise

The correct answer is B, as Manifest Destiny was the belief used to justify westward expansion of America's borders in the 1800s.

The doctrine of Manifest Destiny is a phrase and idea that expresses the belief that the United States of America is a nation destined to expand from the Atlantic coasts to the Pacific. This idea is also used by supporters to justify other territorial acquisitions. The supporters of this ideology believe that the expansion is not only good, but also obvious (manifest) and accurate. This ideology could be summarized in the phrase: "By the Divine or God's Authority".

presidency should be the title