The application pressure gauge shows:
Correct. The application gauge (when present) shows brake-application pressure — useful for spotting brake-system problems on long downgrades.
CDL Practice Question #106
Category: Air Brakes
Why this question matters
This question is one of 71 in our Air Brakes bank. The reasoning above comes directly from the AAMVA CDL Manual, the source document used by every U.S. state DMV. Memorizing the underlying rule — not just the letter answer — is what separates passing on the first attempt from a return trip and another fee.