Never drive so fast or so close that you cannot __________ the necessary distance ahead.

The correct answer is to "see" the necessary distance ahead because visibility is a critical factor in safe driving. Being able to see clearly allows drivers to identify hazards, road conditions, and other vehicles in time to react appropriately. This includes anticipating any potential obstacles or changes in traffic flow that could require a quick response.

Driving at an appropriate speed and distance allows for sufficient reaction time, which is essential for safety. If a driver cannot see far enough ahead, they may not have adequate time to stop or maneuver, leading to accidents. In contrast, the other options, such as accelerating, braking, or signaling, are secondary to the fundamental need for visibility on the road. Without being able to see ahead, even the best brakes or signals would not be effective in preventing a collision. Thus, being able to see ahead is paramount for making informed decisions while driving.