Under what condition is it safe to use high beam headlights?

Answer: C — On rural roads with no other vehicles around and when there are no streetlights

Using high beam headlights is appropriate on rural roads with no other vehicles around and when there are no streetlights because high beams significantly enhance visibility by illuminating a larger area ahead. This condition is particularly beneficial in poorly lit environments, such as rural settings, where there may not be sufficient illumination from streetlights. In contrast, in urban areas with streetlights, using high beams can create glare for other drivers and is unnecessary since streetlights provide adequate visibility. During heavy rain, high beams can reflect off the rain, decreasing visibility rather than improving it. Lastly, using high beams in fog or mist is not advisable, as the light can scatter off the particles in the air, further reducing visibility and possibly causing confusion for other drivers. Thus, the optimal scenario for using high beams is indeed when driving on rural roads without the presence of other vehicles or street lighting.