Which item is commonly listed in transport information?

• A. UN number
• B. Relative density
• C. pH
• D. Solubility

Answer: (A)

Transport information relies on a standardized identifier that quickly and unambiguously identifies a hazardous material. The UN number is that identifier—a four-digit code assigned to dangerous goods that links the substance to its hazard classification, handling requirements, and emergency response guidance. Because this code is recognized worldwide and across different transport modes, it routinely appears on shipping papers, labels, and emergency information for quick identification during loading, transport, and potential incidents. The other properties listed—relative density, pH, and solubility—are chemical characteristics more relevant to product specifications or safety data sheets, not the core items used to identify and manage materials in transit.