What checks must be performed on a vehicle's air brake system?

The correct answer highlights essential checks that ensure the air brake system is functioning properly and safely. Monitoring air pressure is crucial, as it indicates whether the brakes have sufficient power to operate effectively. Checking for leaks is vital because any loss of air can directly compromise braking performance, which could lead to dangerous situations on the road. Additionally, testing the function of the emergency brakes is an integral part of this process, as these brakes serve as a backup system in case the primary brakes fail. By focusing on these critical aspects, the vehicle operator can help ensure safety and reliability in the air brake system, which is particularly important for large commercial vehicles that transport significant loads.