What should you do if you cannot see the road ahead due to heavy fog?

Answer: B — Pull off the road completely until visibility improves

If heavy fog reduces your visibility to the point where you cannot see the road ahead, pulling off the road completely until conditions improve is the safest course of action. This allows you to avoid potential collisions or accidents that could occur if you continue driving in low visibility. By stopping in a safe location, ideally out of traffic, you minimize risk to yourself and other drivers. Staying off the road until visibility improves is important because continuing to drive in fog can lead to a loss of control and increase the likelihood of running into obstacles or other vehicles that may not be visible until it's too late. This decision prioritizes your safety and the safety of others on the road.