What is a breakaway cable?

Answer: B — safety device added to the trailer braking system

A breakaway cable is a safety device that is attached to the trailer's braking system. It is designed to engage the brakes on a trailer in the event that the trailer becomes disconnected from the towing vehicle. This helps prevent the trailer from becoming a hazard on the road and potentially causing accidents. Therefore, options A, C, and D are incorrect as they do not accurately describe the function or purpose of a breakaway cable.