When should you use your horn?

Answer: D — All of the above

Horns should be used as a warning signal to other drivers in certain situations. Using it when another driver is going too slow or following too closely can alert them to your presence and potentially prevent an accident. Similarly, signaling to another driver with your horn can be helpful in avoiding miscommunications on the road. Therefore, using your horn in any of these situations is appropriate and can promote safe driving practices. Option D is the most comprehensive answer as it encompasses all three appropriate uses of a car horn.