When Studying the Impact of a Policy Intervention, Which of the Following

When studying the impact of a policy intervention, which of the following groups should be compared?

A) people's behavior before the policy implementation and after the policy implementation
B) people's behavior before the policy implementation and those who complain about the policy
C) people's feelings about the policy and their behavior after the policy implementation
D) people's feelings about the policy before the policy implementation and whether they complain about the policy after implementation