What device on the trailer will not function if the electrical connection to the towing vehicle is missing or interrupted?

You answered correctly. Both the electronic braking system (EBS) and the lighting system of the trailer rely on the electrical connection to the towing vehicle. If this connection is missing or interrupted, neither the EBS nor the trailer's lights can function, which affects both safety systems and your legal obligations on the road. The traction control system (TCS), however, is typically not found on trailers and does not depend on this connection. Remember, always ensure the electrical plug between the trailer and the towing vehicle is properly connected before driving. This is essential for safe braking and visibility to other road users.