Answer:
C. The Truman Doctrine
Explanation:
The Truman Doctrine is the principle that the US should give support to countries or peoples threatened by Soviet forces or Communist insurrection. First expressed in 1947 by US President Truman in a speech to Congress seeking aid for Greece and Turkey, the doctrine was seen by the Communists as an open declaration of the Cold War. Both the Korean War and the Vietnam War were a clash against Communism.
