Answer :
Final answer:
When there is a major leak in the brake line, the tractor protection valve will close, and the trailer's emergency brakes will engage to prevent further air loss and stop the vehicle safely.
Explanation:
The tractor protection valve will close, and the trailer emergency brakes will come on when there is a major leak in the brake line. The correct answer is c) Emergency. When a leak occurs, the drop in air pressure triggers the tractor protection valve. This valve is designed as a safety feature to prevent air from escaping the entire system, thereby protecting the tractor's air supply and activating the trailer's emergency brakes to bring the vehicle to a safe stop.
