21. How did the theory represented in the quote impact the United States’ policy in Korea and Vietnam?
A. It led directly to the U.S. decision to pull its combat troops out of Vietnam in 1973.
B. It led the U.S. to hope that if North Vietnam became a democracy, other countries would follow.
C. It led directly to the U.S. involvement in Korea and Vietnam to prevent the spread of communism.
D. It led the U.S. to insist on a coalition of allies to fight the war so the U.S. did not have to get involved.