How can you check if the air brake system is functioning properly?

Conducting a brake test and checking for proper air pressure and response is essential to ensure that the air brake system is functioning properly. This involves a series of checks that confirm not only that the air pressure is within safe operating limits but also that the brakes respond appropriately when applied. A proper brake test can help identify issues such as air leaks or insufficient air supply, which could compromise the vehicle's stopping capability.

Specifically, this test typically includes a visual inspection of the pressure gauges, as well as engaging the brakes to ensure they activate as expected. Both the air pressure build-up and the brake application response indicate the overall health of the air brake system. This proactive measure is crucial for driver safety and compliance with regulations.

In contrast, merely inspecting the brake lights, testing the air compressor for noise, or checking tire tread wear does not specifically assess the functionality of the air brake system. While these tasks contribute to overall vehicle maintenance, they do not directly evaluate whether the air brakes are operating safely and efficiently. Hence, option A directly addresses the air brake system's integrity and readiness for safe operation.