Answer:
Option A.
Explanation:
Prevent communism spreading to the United States, is the right answer.
In the year 1947, Harry S. Truman, the then U.S. President promised that the U.S. would accommodate any state resisting communism to limit its spread. This policy of containment came to be recognized as the Truman Doctrine. The Truman Doctrine explained that the U.S. would not respond to isolationism following the Second World War, but willingly take an effective role in the affairs on the global level.
