What should a driver do if a traffic light is not functioning properly?

Answer: C — Treat the intersection as a four-way stop

If a traffic light is not functioning properly, it is important for a driver to treat the intersection as a four-way stop. This means coming to a complete stop and yielding to any other vehicles or pedestrians that have arrived at the intersection before moving through. Option A is incorrect because remaining stopped could lead to a traffic backup and cause confusion for other drivers. Option B is incorrect because proceeding cautiously could be dangerous if other vehicles are not aware of the issue with the traffic light. Option D is incorrect because treating the intersection as a yield could lead to accidents if other drivers do not yield as expected. It is important for drivers to follow the proper protocol in order to ensure everyone's safety at a malfunctioning traffic light.