What must vehicles transporting radioactive material with a Yellow II label display?

Vehicles transporting radioactive material labeled with a Yellow II label must display the word "Radioactive." This is essential for ensuring that anyone interacting with the transport vehicle is immediately informed of the presence of radioactive materials. The labeling acts as a clear and standardized warning, allowing for appropriate safety measures to be taken to minimize exposure risks.

The Yellow II label is specifically designed to communicate the level of radioactivity and the potential hazards associated with the transport of such materials. By mandating the display of "Radioactive," regulatory bodies aim to enhance safety protocols, inform emergency responders, and ensure that proper handling measures are enforced during transport.

Other options, while they might describe dangerous materials, do not specifically convey the nature of radioactivity which is critical in this context. Hence, only the direct labeling with "Radioactive" accurately reflects the concern regarding the nature of the material being transported.