Which of the following is a reason to use your horn?

Using your horn to alert another driver of your presence is an essential safety practice while driving. The primary purpose of the horn is to communicate with other road users and to ensure safety. For instance, if a driver is not aware of your vehicle nearby — perhaps they are about to change lanes or make a turn — using your horn can help prevent potential accidents by making them aware of your presence.

While using your horn to greet someone or express frustration might happen in informal situations, these uses can be seen as distractions and may not contribute to roadway safety. Furthermore, accelerating past another vehicle generally does not necessitate horn usage; it is more important to focus on safe driving and maintaining a proper distance from other vehicles. Thus, using the horn primarily for alerting other drivers is the most appropriate and safety-oriented reason.