What must you observe when you enter a tunnel?

You answered this question correctly. When entering a tunnel, you must switch to dipped headlights even during the day and take off your sunglasses. This is because tunnels, even when well lit, reduce visibility compared to daylight, so dipped headlights help you see and be seen. Sunglasses further decrease your vision in already dimmer tunnel lighting, so they should be removed for safety. Switching on fog headlamps is not required and may actually dazzle other drivers, so that is not correct. Remember: always use dipped headlights and remove sunglasses in tunnels.