On Belgian motorways, which vehicles may use 100 km/h instead of the general 90 km/h for vehicles over 3.5 t?

1. Coaches with a seat belt on every seat and a speed limiter set to a maximum of 100 km/h
2. Every category C goods vehicle with a limiter
3. Any C1 truck under 7.5 t
4. Any vehicle if the left lane is empty