Final answer:
The correct sequence for a pre-trip air brake inspection is to start with the supply pressure test, followed by the service brake test, and finishing with the parking brake test.
Step-by-step explanation:
The correct order of steps for a pre-trip air brake inspection is typically: first, the supply pressure test to ensure the air compressor builds up the correct amount of pressure within the appropriate time; second, the service brake test to check that the brakes respond correctly when applied; and lastly, the parking brake test to verify the parking brakes engage and hold the vehicle when applied. Hence, the answer to your question would be option a) Supply pressure test, service brake test, parking brake test.