How did the domino theory relate to the spread of communism? It was the idea adopted by the United States that if one country fell to communism, other countries would soon follow.
It was the philosophy of the Soviet Union that the spread of communism would occur naturally as workers united around the world.
It was the strategy of the United States to address communism in different countries one by one, hoping to temper its influence.
It was the policy adopted by the Soviet Union to actively introduce and spread communism to one country at a time.