At what pressure does the governor stop pumping air?

Answer: C — 125 psi

The governor stopping the air compressor at 125 psi is based on standard operating procedures for air brake systems in commercial vehicles. When the air pressure in the system reaches around 125 psi, the governor is designed to stop the compressor from pumping air, which helps prevent over-pressurization and potential damage to the system. Maintaining this pressure threshold is critical for safe operation and optimal performance of the air brake system. At this level, the vehicles typically have enough air pressure stored in the tanks to operate the brakes effectively. This ensures drivers have the necessary air for emergency situations while also protecting the integrity of the air brake components. Other pressures listed might not provide the same effectiveness or safety, as the common regulation for commercial motor vehicles is to hold the cut-out point at 125 psi, which is recognized as an industry standard.