In which situation should you dim your headlights?

Answer: C — When you see another vehicle approaching from the opposite direction

Dimming your headlights is important for maintaining safety and visibility on the road. When you see another vehicle approaching from the opposite direction, it's crucial to dim your headlights to avoid blinding the oncoming driver. High beams can be very powerful and can obstruct the vision of drivers coming towards you, potentially leading to dangerous situations. In contrast, while dimming headlights can also be appropriate when following another vehicle closely or in urban areas, the primary concern with oncoming traffic is to ensure that both you and the other driver can see clearly without being compromised by excessive glare. In bright daylight, the use of headlights is often not necessary, and high beams can be detrimental. Thus, the action of dimming headlights is vital specifically when approaching another vehicle head-on.