Which item should be further investigated for hazardous materials?

The item that should be further investigated for hazardous materials is the box with a Class 4 flammable liquids label. Class 4 hazards are specifically related to flammable solids, spontaneously combustible materials, and dangerous when wet materials. The presence of a label indicating that the contents are flammable liquids suggests a significant risk and necessitates careful handling to prevent accidents, such as fires or explosions.

Identifying a Class 4 label is critical because it provides specific information about the nature of the contents and the precautions that must be taken. In the context of hazardous materials, it is essential to adhere to safety regulations and protocols to ensure the safety of all personnel involved. Therefore, this item warrants immediate attention and investigation to ascertain its contents and determine appropriate handling measures.

While the other items could present hazards, they do not provide a clear indication of the risk associated with them as the Class 4 label does, making further investigation of the labeled box imperative.