In heavy traffic, when should you use your horn?
Answer: A — To warn drivers in front of you
You should use your horn to warn drivers in front of you when traffic is heavy. Honking out of frustration (option B) is not recommended as it does not solve the traffic issue and can potentially escalate the situation. Honking at cyclists (option C) should also be avoided as it can startle them and cause accidents. Greeting other drivers with a horn (option D) is not necessary and can be considered distracting while driving. It is important to use your horn responsibly and only when necessary for safety reasons.