How can you check the state of wear of the drawbar or the turntable of a full trailer?

You answered correctly. To check the state of wear of the drawbar or turntable of a full trailer, you should briefly start up with the towing vehicle while the trailer is secured with the parking brake. This puts the load on the coupling parts, allowing you to feel or hear excessive play or movement that would indicate wear. Using the parking brake ensures the trailer stays firmly in place during the test. This is an important safety check before driving with a trailer, as worn coupling parts can lead to dangerous situations on the road. The other options are not correct methods for checking wear in this context.