Which trailer combination is normally within ordinary category B scope in Denmark without an extra trailer category?

1. A category B vehicle with a light trailer up to 750 kg, subject to the vehicle's limits
2. A category B vehicle towing any trailer if the driver is over 25
3. A 3,500 kg car towing a 3,500 kg trailer as ordinary B
4. A bus towing a trailer because the driver has category B