What must you remember when coupling up a trailer?

You answered correctly because both points 1 and 2 are important when coupling a trailer in Germany. The rule about not connecting coupling parts with different colors ensures that the trailer’s braking and electrical systems are matched correctly, preventing malfunctions. Releasing the parking brake and removing wheel chocks after the trailer is coupled is essential for safe movement; leaving them on could cause accidents or damage. The choice about first connecting the emergency line is not the primary step and therefore not included in the main rules for coupling up a trailer. Remembering these steps helps ensure the trailer is safely and properly connected before driving.