Which federal regulation governs hazardous materials transportation?

The choice regarding 49 CFR (Code of Federal Regulations) Part 172 is correct because this section specifically outlines the requirements for the labeling, marking, and placarding of hazardous materials that are being transported. It establishes the necessary standards for ensuring that hazardous materials are properly identified to protect public safety and facilitate safe transportation. This part of the regulations provides detailed instructions on classification, packaging, and communicating the hazards related to the materials, which are critical for emergency responders and transporters alike.

The other options do not pertain to the transportation of hazardous materials. For instance, 49 CFR Part 101 deals with general provisions applicable across various transportation regulations but does not specifically focus on hazardous materials. 49 CFR Part 150 relates to regulations for the use of explosives and does not cover the broader category of hazardous materials. Finally, 54 CFR is not a valid code within the context of hazardous materials transportation. Therefore, 49 CFR Part 172 is the appropriate regulation governing this domain.