How should you respond to a traffic signal that is malfunctioning?

Answer: C — Treat it as a four-way stop.

When a traffic signal is malfunctioning, treating it as a four-way stop is appropriate because it helps ensure safety and order at the intersection. In such situations, all vehicles approaching the intersection must come to a complete stop and yield to other traffic based on the rules of right-of-way. This method allows drivers to assess the situation and decide how to proceed safely, considering the movements of other vehicles and pedestrians. This approach is consistent with standard traffic regulations, which dictate that when signals are out of order, the intersection operates as if it has stop signs posted for all directions. This helps prevent confusion and potential accidents that could occur if drivers were to ignore the signal or proceed recklessly without stopping.