Which of the following is NOT a flammable solid?

Cement is not considered a flammable solid. Flammable solids are materials that can easily ignite and sustain combustion under normal conditions. Sodium, magnesium, and aluminum powder are all highly reactive and can ignite when they come into contact with moisture or certain conditions, allowing them to burn readily.

In contrast, cement is primarily used as a binding agent in construction materials like concrete and does not possess the characteristics required to be classified as a flammable solid. It is stable, non-reactive, and does not ignite easily. Understanding the properties of these materials is crucial for safety, especially when dealing with hazardous materials in various environments.