Question

The domino effect, in reference to U.S. policy in Indochina during the Cold War, refers to which of these? A. the strategy of the U.S. military to defeat communism in Vietnam before attacking neighboring countries B. the fear among U.S. policy makers that if communism succeeded in Vietnam, it would sweep through the rest of the region C. the propaganda distributed by the Northern Vietnamese which argued that U.S. aggression in Vietnam was only a game to Americans D. the manner in which the U.S. military arranged its ground troops deployed to Vietnam

Answer 1

B. The fear among U.S. policy makers that if communism succeeded in Vietnam, it would sweep through the rest of the region.

The domino effect, is the idea that if one country falls to communism, other countries would soon fall, like toppling a line of dominoes. That's why we got involved in Vietnam, to prevent that.