What happens if a brake application is made with a ruptured control line?

Answer: C — The trailer brakes will not be applied

When a brake application is made with a ruptured control line, the critical aspect to understand is how air pressure is transmitted through the braking system. In this scenario, the control line is responsible for conveying air pressure from the tractor to the trailer's brakes. If this line is ruptured, air cannot properly flow to the trailer, leading to a failure in the braking system for that trailer. As a result, the trailer brakes will not engage because they do not receive the necessary air pressure to activate. This can significantly affect the vehicle's stopping capability, as the trailer would essentially remain unbraked while the tractor tries to slow down or stop. Understanding this mechanism is crucial for safe vehicle operation and highlights the importance of ensuring that all components of the air brake system are in good working order before operation.