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

Your selected combination of requirements is correct. According to German traffic regulations, before coupling a semi-trailer, it is essential that the fifth wheel is unlocked and opened, allowing for proper connection. Additionally, it is crucial that both the fifth wheel and the coupling are at roughly the same height to facilitate a smooth and secure attachment.

These steps ensure not only that the semi-trailer is safely connected but also that the vehicle can operate effectively once hitched. Neglecting any of these steps could lead to an insecure connection and pose a risk during driving, which is why these specific requirements are emphasized in the regulations.