What Was the Role of the Truman Doctrine

What was the role of the Truman Doctrine?

A) It was an American commitment to using atomic bombs as a first line of defense.
B) It promised that the United States would only intervene in the Western Hemisphere if necessary.
C) It committed the United States to help "free peoples" facing pressure from communism.
D) It was a policy at odds with the "domino theory" and, thus, proved widely unpopular at the time.
E) It made it clear that the United States would not get involved in the affairs of Europe or Asia again.