Final answer:
Option (a), Americans feared communist takeover due to political tensions with communist countries, fear of communism spreading globally, and concerns over economic instability leading to domestic acceptance of communist ideas.
Step-by-step explanation:
Americans were scared that communists would try to take over the country primarily due to political tensions between the US and communist nations, the perceived threat of communism spreading from other countries, and the fear that economic instability could be exacerbated by communist ideologies.
Political tensions following World War II, such as those manifesting in the formation of NATO and the Warsaw Pact and the implementation of US containment policy, spotlighted the growing global divide. Instances including the victory of the Chinese Communist Party, the Korean War, and the Soviet blockade of West Berlin highlighted the very real presence of communism on the world stage.
The internal climate within the United States was charged with fear during the first Red Scare and following into the 1950s. The presence of letter bombs, like those discovered at a New York City post office, and the explosion at the home of U.S. Attorney General A. Mitchell Palmer, cemented the fear of communists and their perceived intent to overthrow the government. This fear was aggravated by economic hardship, where the attraction of socialist and communist ideas among impoverished citizens in post-war Europe reflected concerns back in the USA about domestic vulnerabilities.