Final answer:
Americans became increasingly frightened by nuclear war after World War II. Hence the correct answer is option C
Step-by-step explanation:
After World War II, Americans became increasingly frightened by C) Nuclear war. The use of atomic bombs on Hiroshima and Nagasaki during the war had demonstrated the destructive power of nuclear weapons, leading to widespread fear of their use in future conflicts. This fear was further fueled by the escalation of the Cold War between the United States and the Soviet Union, resulting in a heightened concern about the possibility of a nuclear war.