There is a translation fault in answer B.
It has to be:
"The parking lights and the rear fog light must be lit".
So answer B is wrong in that case.

There is a thick fog and you park the car on the road.
What’s wrong?

A. The rear fog light may be on.
B. The parking lights and the red rear lights must be lit.
C. The front fog lights may be on.

Thw question is "What's wrong ?"

Can you please explain what is wrong in "The parking lights and the red rear lights must be lit."

In the book on page 73 it is clearly mentioned in the section "Waiting and Parking"

1. What lights must be used .

I think the question is wrong all of the three points are correct. Please explain in detail.