What action should you take if a vehicle comes towards you with high beams on?

Answer: B — Flash your headlights quickly a couple of times

Flashing your headlights quickly a couple of times is the most appropriate and safest response when encountering a vehicle with high beams on. Turning on your fog lights or honking your horn can be distracting for both you and the other driver, and may not effectively communicate that their high beams are blinding you. Turning off your headlights should not be done as it will leave you completely without any lights, making it difficult for other drivers to see you in dark or low visibility situations. It is important to always prioritize safety on the road and flashing your headlights quickly is the best option in this scenario.