When driving in fog, you should use
- parking lights.
- parking lights and high-beam headlights.
- low-beam headlights. ✓
- high-beam headlights.
Answer: C. low-beam headlights.
In fog you should drive with your low-beam headlights on.
Why this is the answer
The handbook's fog section tells you to make sure the full lighting system is on and to use low beams. It explains the reason: high beams bounce off the moisture droplets in the fog and make it harder to see. If the truck has fog lights, they are used in addition to the low beams, not instead of them. Parking lights alone would not meet the instruction to have the full lighting system turned on.
Why the other answers are wrong
- A. parking lights. — Parking lights alone leave the rest of the lighting system off, and the handbook asks for the full lighting system to be on in fog.
- B. parking lights and high-beam headlights. — Adding high beams to parking lights still leaves you with the glare problem, since high beams reflect off the moisture in the fog and reduce how far you can see.
- D. high-beam headlights. — High beams are the wrong choice in fog because the light bounces off the water droplets in the air and makes visibility worse, not better.
Remember it
Think of fog as a wall of tiny mirrors: keep the beams low so the light stays on the road instead of bouncing back at you.