When does a Category C goods vehicle towing a trailer generally require Category CE under Road Traffic Act Art. 150a?

1. Whenever the trailer has two or more axles, even if its mass is 500 kg
2. Whenever the trailer has no overrun brake, regardless of mass
3. Whenever the trailer's maximum permissible mass exceeds 750 kg
4. Whenever the journey is international, even with a 500 kg trailer