When driving, the speed must be adjusted to enable stopping within what?

The correct choice emphasizes the importance of adjusting your speed based on visibility and the conditions of the road ahead. When driving, it is crucial to maintain a speed that allows you to stop safely within a distance you can clearly see ahead of you. This means that if there's an obstacle or sudden change in traffic conditions, you have enough time to react and bring your vehicle to a complete stop.

Driving at a speed that enables you to stop within a clear distance ahead helps prevent accidents, as it ensures the driver is in control of their vehicle and can respond effectively to any hazards. This principle is part of defensive driving techniques, aiding in keeping both the driver and others on the road safe.

The other options provided do not encompass the fundamental safety guideline of adjusting speed based on visible distance, indicating a more rigid or impractical approach to driving that could lead to dangerous situations.