When driving in dense fog, heavy tropical downpours, or thick smoke where visibility drops below 50 metres, which lights must be used?

1. Low-beam headlights (feux de croisement) and front/rear fog lights if equipped
2. High-beam headlights (feux de route) to penetrate through the fog
3. Position lights (feux de position) only, with headlights switched off
4. No lights are necessary during daytime rain