During a pre-trip air brake check for leaks, which steps should you perform?

Answer: D — Start the engine, observe gauges, listen for audible leaks around valves and hoses, and perform a brief air-leak test by applying the brakes and noting any rapid pressure drop.

This checks your ability to perform a thorough leak check on the air brake system during a pre-trip, combining both visual/audible inspection and a live-pressure test. Start the engine so the compressor builds pressure and watch the gauges to confirm the system reaches the normal operating range and that the governor cuts in and out properly. Listen for any hissing or leaks around valves, hoses, and fittings—those audible cues can reveal leaks that aren’t obvious to the eye. Then run a brief air-leak test by applying the brakes and noting any rapid drop in air pressure; a healthy system should hold pressure during this test with only a small, gradual change. This combination of watching gauges, listening for leaks, and testing pressure under brake application covers all essential leak-check steps. Other options fall short because they either skip the gauge check, skip the brake test, or ignore the air brake system altogether.