When driving under especially unfavourable visibility conditions, is it compulsory to switch on the rear fog light?

When driving under especially unfavourable visibility conditions, is it compulsory to switch on the rear fog light?
A)No, it is optional only.
B)Yes, and it is also compulsory to switch on the full-beam headlights.
C)Yes, to indicate its position to other road users.Correct
FRONT FOG LIGHT:
- Its installation and use is NOT compulsory.
- It shall be white or selective yellow in colour.
- It shall be used voluntarily in the case of fog, heavy rain, snowfall, clouds of smoke or dust, or in circumstances similar to the above.
- It may also be used on narrow roads with many bends — that is, those with a carriageway width of 6.5 m or less that are marked with "dangerous bends" signs.
REAR FOG LIGHT:
- Its installation and use is compulsory.
- It shall be red in colour.
- It shall be used, compulsorily, in the case of THICK fog, VERY heavy rain, HEAVY snowfall, or DENSE clouds of smoke or dust.
The front fog light, during the day, may be switched on with only the sidelights, but may also be used together with the dipped or full-beam headlights. At night, it shall be used at a minimum with the dipped headlights.
The rear fog light, during the day, shall be used at a minimum together with the front fog light or the dipped headlights. At night, at a minimum with the dipped headlights.