The 24-hour emergency response phone number on the shipping paper:
Correct. The 24-hour emergency contact must be a person knowledgeable about the materials, available 24/7. Many shippers contract CHEMTREC or similar.
CDL Practice Question #257
Category: Hazmat
Why this question matters
This question is one of 68 in our Hazmat 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.