You should check the air-system pressure build-up time during pre-trip:
Correct. In dual air-brake systems, the air should build from 85 to 100 psi within 45 seconds with the engine at governed RPM.
CDL Practice Question #168
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.