Which term describes materials that may pose an unreasonable risk to health, safety, or property during transport?

Answer: B — Hazardous Material

The term that fits the transport context is hazardous material. In transportation safety, anything that due to its properties could pose a risk to health, safety, or property when moved is labeled as a hazardous material. This designation triggers specific regulatory requirements: proper packaging, correct labeling and placarding, shipping papers, trained personnel, and emergency response information. That’s why this term is the precise, official way to describe materials that require special handling during transport. The other terms aren’t the standard regulatory language used for hazmat in transit. Shortened “Haz” isn’t a recognized label, “Dangerous Substance” isn’t the official term (the common international phrasing is “dangerous goods” or “hazardous materials”), and “Regulatory Item” doesn’t describe hazmat at all.