If a policeman tells you to stop and it contradicts a traffic sign or signal, you should:

Answer: B — Listen to the policeman

In this scenario, when a policeman instructs you to stop, it is important to listen to the policeman even if it goes against a traffic sign or signal. Law enforcement officers have the authority to direct traffic and ensure the safety of the public. By following the instructions of the policeman, you are helping maintain order on the road and prevent potential incidents. It is crucial to prioritize the directions given by the officer in such situations to ensure the safety of everyone on the road.