Self-reactive materials are:

• A. Phosphorus
• B. Wetted explosives
• C. Readily combustible solids
• D. Self-reactive materials

Answer: (D)

Self-reactive materials are substances that can undergo a strongly exothermic decomposition on their own, without needing an external energy source to start. They may heat up, release gases, and, if confined, build pressure that can lead to a fire or explosion. This self-decomposition behavior is what defines them as a distinct hazard, so naming the category itself is the correct description. The other options describe specific materials or different types of hazards (for example, some substances ignite readily, some are treated to reduce sensitivity, but none define the self-decomposition property that characterizes self-reactive materials).