What is required when visibility is substantially reduced due to fog, rain, or snowfall?

Answer: B — Use of low-beam headlights is required

When visibility is substantially reduced due to conditions such as fog, rain, or snowfall, the use of low-beam headlights is required as they provide adequate illumination without causing glare that can impair the vision of other drivers. Low-beam headlights are designed to illuminate the road directly in front of the vehicle and ensure that the driver can see and be seen in adverse weather conditions. In these situations, high-beam headlights can create excessive glare and reflection that may worsen visibility for both the driver and other road users. Therefore, relying on low-beam headlights helps maintain safety by ensuring that everyone on the road can navigate effectively, especially in low-visibility scenarios.