Under what condition should motorists use their vehicle's high beam headlights?

Answer: D — When following closely behind another vehicle

In residential areas, motorists should use their vehicle's low beam headlights to avoid blinding other drivers. In foggy weather or during snowstorms, the high beam headlights may reflect off the precipitation and decrease visibility. When following closely behind another vehicle, motorists should use their low beam headlights to avoid distracting the driver in front and to maintain a safe following distance. Therefore, high beam headlights should only be used when driving in open roads without any vehicles in close proximity.