A two-axle trailer with overrun brakes and fifth-wheel steering is parked on a slope. How must it be secured against rolling?

Your combination of answers is correct. According to German traffic regulations, when parking a trailer on a slope, it is essential to secure it properly to prevent any rolling. Engaging the parking brake ensures that the trailer is held in place by the brake system, while placing a wheel chock underneath a rear wheel provides an additional layer of security against movement. Both methods are necessary for adequate safety and compliance with traffic regulations. Supporting the forked draw-bar is not necessary for securing the trailer against rolling; instead, focusing on the parking brake and wheel chocks is sufficient and recommended.