What is the main function of the application air gauge in a vehicle?

Answer: C — To show the amount of applied brake pressure

The main function of the application air gauge in a vehicle is to show the amount of applied brake pressure. This gauge is specifically designed to monitor the air pressure that is being used in the braking system. When the driver applies the brakes, this gauge reflects the pressure in the air brake system, allowing the driver to have a clear indication of how much braking force is being applied. Monitoring the applied brake pressure is crucial for ensuring safe operation, as it helps the driver understand the braking system's condition and effectiveness. Adequate monitoring can prevent brake failure due to insufficient air pressure and allows the driver to make informed decisions regarding braking in various situations. Other gauges serve different functions, such as measuring fuel consumption, indicating general air pressure levels, or providing temperature readings, which do not pertain to the application air gauge's primary function related to braking.