Technician A says that most current highway tractors use a 3-line TP valve.Technician B says that a 2-line TP valve will remain OFF (closed) until the trailer air supply dash button is depressed.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

TP Valve

Temperature Pressure Relief Valve; a safety device on water heaters to release water should either the temperature or pressure get too high, preventing potential explosions.

Trailer Air Supply

The system that provides compressed air from the tractor to the trailer for operating air brakes and other pneumatic systems.

Highway Tractors

Trucks designed primarily for long-haul transportation over highways, often equipped with sleeping compartments.