What should you do when it starts to rain heavily?

Answer: C — Slow down and drive cautiously

When it starts to rain heavily, it is important to slow down and drive cautiously because the roads become slippery and it may be difficult to see clearly. Continuing at the same speed (option A) could lead to losing control of the vehicle. Switching your headlights on (option B) is important, but it is not the most important action to take. Pulling over to the side of the road (option D) may be necessary in some situations, but it is not always the best solution. It is safest to reduce your speed and drive with caution until the rain stops or the driving conditions improve.