Answer :
Final answer:
A tractor protection valve is considered defective if it exhausts air when the trailer supply valve is closed, pointing to the tractor protection valve itself as the source of the issue.
Explanation:
The question is about identifying when a tractor protection valve is defective. Specifically, it concerns a scenario where the trailer supply valve is closed, also known as being pulled out, and determining where air would exhaust in the case of a defective tractor protection valve.
If air exhausts from the tractor protection valve itself when the trailer supply valve is closed, this would indicate that the tractor protection valve is defective. The tractor protection valve's primary function is to protect the air brake system's integrity on the tractor when the trailer is disconnected or if there is a loss of air pressure in the trailer system.
It should not be venting air in the closed position. In this context, the correct answer to the student's question would be: c) Tractor protection valve itself
