Practice question Which regulation defines the H endorsement knowledge topics? 49 CFR 383.121Only when traveling interstateOnly if the trip exceeds 100 milesOnly when the driver chooses to do so Answer: A — 49 CFR 383.121 The correct answer is shown above. Try the full quiz for additional practice. Practice more: TN CDL Hazmat Practice Questions - Tennessee CDL Hazardous Materials Endorsement Test Exam →