Answer:
The Truman Doctrine, Marshall Plan and the Domino Theory were the foreign policies of American, they all were meant to stop communism from spreading.
Truman doctrine gives the proposal to help democratic countries who reject the communism and the Marshall Plan is the actual help that the US sent to these countries to develop in machinery and other materials to rebuild and be free from communist.
Where the Domino Theory was given by President Dwight D. Eisenhower which later on led to the war in Vietnam between North Vietnam, Viet Cong and South Vietnam ally to America in the 1970s.
