What is correct when coupling a full trailer?

The selected combination is correct because both options 1 and 2 are essential for safely coupling a full trailer. According to German traffic laws, it is important that the driver has a clear line of sight to ensure safe positioning and operation. This visibility helps prevent accidents by allowing the driver to be aware of any obstacles.

Additionally, having a warning system in place to alert the driver to road users or obstacles that may not be visible is crucial for safe maneuvering. These precautions help ensure that the coupling process is conducted safely and reduces the risk of collisions.

Option 3 is also important, as it ensures that the drawbar is securely locked into the hitch, which is vital for the stability of the trailer while driving. Therefore, understanding the significance of all relevant options is essential for ensuring safety when coupling a full trailer according to German traffic regulations.