Under the United Nations Labeling System, which substance would be labeled as 5?

In the United Nations Labeling System, the label marked with the number 5 specifically identifies oxygen-yielding substances. This category is critical in the context of hazardous materials because these substances are capable of providing oxygen to support combustion, which makes them highly reactive and potentially dangerous when exposed to flammable materials.

Understanding that oxygen-yielding substances can enhance the intensity and spread of fires is essential for proper handling and response during emergencies. This classification serves to alert responders and handlers to the potential risks associated with these materials, facilitating appropriate safety measures and emergency protocols.

The other options refer to different hazards: flammable solids are marked with a different label, non-flammable gases have their own classification, and corrosive substances fall into yet another category entirely. Knowing how each substance is categorized helps ensure that individuals in hazard response situations can quickly recognize the nature of the risks they face.