Which requirements must be fulfilled before coupling a semi-trailer?

The selected combination is correct because both requirements ensure that the semi-trailer can be safely and securely coupled to the towing vehicle.

1. The fifth wheel must be unlocked and opened: This is essential for allowing the coupling mechanism to operate effectively. If the fifth wheel is not in the correct position, the trailer cannot be securely attached.

2. The fifth wheel and coupling must be at roughly the same height: This is crucial for proper alignment. If the heights do not match, it can lead to instability while driving and increase the risk of accidents.

While option 3, which states that all tube and cable connections must be established, is also important, it is not necessary to couple the semi-trailer as a first step. This option is relevant but comes after the initial coupling requirements are fulfilled. Understanding these requirements aligns with the rules set out in the German Road Traffic Regulations, which emphasize safety and proper equipment handling.