When is it necessary to use your horn while driving?

Answer: B — To alert another driver of your presence in a dangerous situation

Using your horn is primarily necessary to alert another driver of your presence in a dangerous situation. This function serves as a critical safety tool to prevent accidents and enhance awareness on the road. For example, if a driver is about to change lanes without noticing your vehicle or is encroaching into your lane, using the horn can get their attention and potentially avoid a collision. In contrast, using the horn to express frustration or to greet friends is inappropriate and can contribute to road rage or distractions. Additionally, there is no requirement or purpose for using the horn when parked, as it does not contribute to safety or communication with other road users in that context.