C) The protection of free speech, is the correct answer.
Within the US, the Cold War was a state political and military tension after WWII, based on the threat of nuclear war, so D is not the answer. As well, McCarthyism was a product of the cold war and was characterized by investigating citizens on the charges of treason, so B is not the answer either. The arms race is another characteristic of the Cold War, due to the military tension of the cold war, therefore A is not the answer either. That leaves C as the correct answer, which makes sense considering the prevalence of McCarthyism during the era.
