What should the front and rear air pressure gauges read before operating the M1120?

Answer: B — 100 psi

Before operating the M1120, the front and rear air pressure gauges should read 100 psi. This pressure is essential to ensure that the air brake system is functioning correctly and safely. Maintaining appropriate air pressure is crucial for the reliable operation of the vehicle since inadequate pressure can compromise braking efficiency and overall safety. The requirement for 100 psi strikes a balance between adequate braking performance and the operational limits of the air system. If the air pressure is too low, it can lead to brake failure, while pressure that exceeds design specifications can stress the air system components. Therefore, monitoring to ensure that air pressure readings are around 100 psi before operation helps prevent potential safety hazards during driving.