With very heavy rain, is it mandatory to use the rear fog light?

A)Yes.Correct
B)No, it is only optional.
C)No, I can only use it in case of very thick fog.
REAR FOG LIGHT:
- Its installation and use is mandatory.
- It will be red.
- It will be used, mandatorily, in case of THICK fog, VERY heavy rain, HEAVY snowfall or DENSE clouds of smoke or dust. The rear fog light, during the day, will be used at minimum together with the front fog light or the low beam. At night, at minimum with the low beam.
- Its installation and use is mandatory.
- It will be red.
- It will be used, mandatorily, in case of THICK fog, VERY heavy rain, HEAVY snowfall or DENSE clouds of smoke or dust. The rear fog light, during the day, will be used at minimum together with the front fog light or the low beam. At night, at minimum with the low beam.