The rear fog lamp:

1. It is obligatory to install fog lights in buses only.
2. Is turned-on automatically when it is foggy.
3. Correct answer: the rear fog lights can only be turned on if the front lights are on.
4. Is turned-on only while driving in reverse.

WhyThe rear fog lamps can be turned on only together with the front lights. They do not work on their own in fog.