Final answer:
To check the air compressor governor 'cut in' and 'cut out' pressures, you need to run the engine at a fast idle, step on and off the brake to reduce the tank pressure, and monitor the air pressure gauge.
Step-by-step explanation:
To check the air compressor governor "cut in" and "cut out" pressures, the correct answer is D) all of the above.
Running the engine at a fast idle allows the air compressor to build up pressure in the tank, which triggers the "cut in" pressure. Stepping on and off the brake reduces the tank pressure, causing the governor to reach the "cut out" pressure. Monitoring the air pressure gauge helps to determine when these pressure points are reached.