When driving in very heavy rain, which fog lights will we use?

When driving in very heavy rain, which fog lights will we use?
A)The front ones mandatorily, the rear ones optionally.
B)The front ones optionally and the rear ones mandatorily.Correct
C)Both the front and rear ones mandatorily.
It is not mandatory for vehicles to be fitted with front fog lights, so their use is optional. The same does not apply to the rear ones, so in the case of VERY heavy rain it will be mandatory to have them switched on.

FRONT FOG LIGHT:
- Its installation and use is NOT mandatory.
- It will be white or selective yellow.
- It will be used, voluntarily, in the case of fog, heavy rain, snowfall, clouds of smoke or dust, or in similar circumstances.
- It may also be used on narrow roads with many curves, that is, those with a carriageway 6.5 m wide or less, signposted with "dangerous curves" signs.
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.
Front fog lights, during the day, may be on with only the position lights, but may also be used together with low-beam or high-beam lights. At night, they will be used at least with low-beam lights.
Rear fog lights, during the day, will be used at least together with the front fog lights or low-beam lights. At night, at least with the low-beam lights.