The post–World War II Red Scare went through various phases, and examining the choices provided:
A. It became more difficult to monitor citizens. - This is not typically true in the context of the Red Scare, as monitoring increased during this time.
B. The U.S. created laws to deal with the communist threat. - This is accurate, as various laws were enacted to counter perceived Communist threats, such as the McCarran Internal Security Act.
C. The government began to monitor people who weren’t communists. - While the government did expand its surveillance, this statement needs clarification as it implies broader suspicion that was not entirely directed toward non-communists but included various leftist groups and individuals.
D. Surveillance of American citizens got more intense. - This is also true, as the government did ramp up surveillance and investigations into individuals suspected of communist sympathies or activities.
In summary, while options B and D are accurate in reflecting the increase in laws and surveillance activities, option B (the creation of laws) may reflect a systematic response, while D (intensified surveillance) better captures the atmosphere and actions of the government over time. Thus, both B and D could be correct, but based on the context of your question's focus on change over time, D may be the most direct choice illustrating how the Red Scare evolved.