Your tractor is equipped with a K 80 coupling system with manual locking. What must you ensure when coupling a trailer?

Your answer correctly includes the importance of locking the retainer on the coupling system after coupling the trailer, as this ensures that the trailer is securely attached and prevents it from disconnecting while in motion. It is also correct to adjust the height of the trailer coupling, as this ensures a proper fit and alignment between the tractor and the trailer, which is essential for safe towing.

The third option, lubricating the coupling system, is not required each time before use according to German traffic rules, but it is advisable for maintaining the coupling system in good working order. Understanding and applying all relevant parts of these regulations is crucial for safe operation on the road.