Lights, visibility, and being seen
Fog and heavy rain call for specific lights
In fog, heavy rain, or very low visibility, use the right lights — but don't use rear fog lights in mild conditions.
What to watch for
The question mentions fog, heavy rain, snow, or very reduced visibility.
The rule
The rule explains exactly how to answer any question of this type — and why the obvious wrong answer fails.
See the rule →Common trap
Don't use rear fog lights in light rain — they dazzle drivers behind you.