Why should you use the permanent brake (retarder) of your motor vehicle?

You are correct in selecting that the permanent brake (retarder) operates without wear and can relieve the service braking device. In German traffic rules, the retarder is designed to provide continuous braking force without wearing down the main service brakes, which helps prevent overheating and reduces maintenance needs. However, the retarder is not intended to bring the vehicle to a complete stop; the main brakes are still required for stopping the vehicle fully. This is why the first two points are correct, and the third is incorrect. Understanding this helps ensure safe and efficient braking, especially on long descents.