In which situation is it appropriate to use your vehicle's horn?

Using your vehicle's horn to alert a driver of your presence is appropriate and serves a crucial safety function. The horn is primarily a tool for communication on the road, helping to prevent accidents by getting the attention of other drivers, especially in situations where visibility may be poor or when another vehicle is not aware of your presence. This use of the horn is guided by the principle of promoting safety and awareness among all road users, ensuring that potential hazards can be addressed quickly.

The other options do not align with the intended purpose of the horn. Expressing frustration is not a constructive use of the horn and can lead to road rage or escalate tensions. Greeting pedestrians or signaling to a friend does not prioritize safety and may confuse other drivers or pedestrians regarding your intentions. Therefore, the primary and most acceptable use of the horn is to enhance awareness on the road, making option B the correct choice.