When should you use your horn?

Using your horn is primarily intended for safety and communication purposes on the road. The correct answer highlights the importance of using your horn to alert other drivers when necessary, such as when you need to warn them of your presence or of a potential hazard. This can be particularly crucial in situations where visual signals may not be sufficient, such as when another driver is merging into your lane without seeing you or when you are approaching an intersection where someone may not notice you.

The other options do not align with the primary function of a vehicle's horn. For instance, greeting friends can be seen as unnecessary and potentially distracting. Using the horn just in traffic jams or to signal that you are stopping could lead to confusion for other road users, as these scenarios do not typically warrant horn use according to traffic safety guidelines. The horn should serve as a tool for signaling in urgent or safety-related situations rather than for casual interactions or non-critical signaling.