James K. Polk cited which U. S. policy to justify Manifest Destiny?

(A) The Monroe Doctrine

(B) Washington's pledge of neutrality

(C) The Missouri Compromise

(D) The American System

(E) The Preemption Act

James K. Polk cited the "Monroe Doctrine" to justify Manifest Destiny, since this Doctrine held that the United States was the main power in the Americas--meaning that it was the "right" and "destiny" of the US to expand all the way to the Pacific Ocean.