Final answer:
The foot brake sends air to all the brakes on the vehicle, including the trailer(s).
Step-by-step explanation:
In terms of braking systems, the foot brake and the trailer hand valve both play important roles. The foot brake is responsible for sending air to all the brakes on the vehicle, including the trailer brakes. This means that when the driver steps on the foot brake, air pressure is applied to both the vehicle and trailer brakes to slow down or stop the vehicle.
The trailer hand valve, on the other hand, is typically used to test the trailer brakes. It allows the driver to manually apply pressure to only the trailer brakes, without affecting the vehicle brakes.
Therefore, the correct statement is: The foot brake sends air to all the brakes on the vehicle, including the trailer(s).