What must you check before coupling up a multiple-axle trailer?

Your combination of answers is correct. Before coupling a multiple-axle trailer, it is essential to ensure that the trailer is secured against rolling away, which can be accomplished by using the parking brake or wheel chocks. This is crucial for safety, as an unsecured trailer can cause accidents.

Additionally, checking whether the towing fork is correctly adjusted is also necessary. An improperly adjusted towing fork can lead to poor handling or even detachment while driving, posing significant risks on the road.

These precautions are outlined in German traffic regulations, emphasizing the importance of thorough checks prior to coupling a trailer to ensure the safety of all road users.