According to the documents below, what evidence points to the idea that the United States' fear of the spread of communism was a possible cause of...

Not all of these documents show that the Cold War started because the United States was afraid that communism would spread around the world.  In fact, only two of these documents give evidence of this idea.  The other documents make different points about the Cold War.

The first document that gives evidence of this idea is Document B.  In the second paragraph of this document, Churchill warns that the Soviets are trying to expand.  He warns that they have “fifth columns” in every society ready to whatever Moscow wants.  He explicitly says that the Soviets want to spread communism across the world, that they want the “indefinite expansion of their power and doctrines.”  To the extent that Americans agreed with Churchill’s analysis, this document shows that fear of the spread of communism helped cause the Cold War.

The other document that supports this idea is Document D.  Here, President Truman is explaining why he is giving aid to Greece and Turkey under the Truman Doctrine.  He says that Greece is under attack by communist rebels and that it needs help so that those rebels do not win.  If the communists win in Greece, he says, they might win in Turkey and then spread through the Middle East.  Clearly, Truman is giving aid to foreign countries (part of what the US did in the Cold War) because he fears that communism will spread.

Between them, these two documents show that Churchill had warned the Americans that the Soviet Union wanted to expand its power and that President Truman instituted the Truman Doctrine (that the US would help any country threatened by communism) because he did not want this to happen.  This is evidence that the Cold War started because the US feared that communism would spread around the world.