About Trailer coupling and licence plate: which statement is correct?
A trailer may have both a breakaway braking device and an auxiliary coupling for extra safety.
A light trailer (up to 750 kg) gets a yellow plate with its own registration; a heavy trailer (above 750 kg) gets a white plate with the car's registration.
An auxiliary coupling is a valid alternative to a breakaway braking device for any trailer, regardless of weight.
The same up-to-750-kg rule applies to bike carriers that hide the car's licence plate from view.
Explanation
Book p.231 - the same up-to-750-kg rule applies to bike carriers that hide the car's licence plate from view. They get a white plate with the same registration as the car.