Which of the following is an example of a combustible material?

The chosen answer, paper, is classified as a combustible material because it readily ignites and burns when exposed to sufficient heat. Combustible materials are those that can catch fire and contribute to flames, often doing so at relatively low temperatures. Paper, being composed of cellulose fibers, is designed to absorb moisture and is flammable, making it easily ignitable in various environments.

In contrast, materials like metal, glass, and concrete do not have the same properties. Metals, while they can catch fire under extreme conditions (e.g., when in fine dust form or when molten), do not easily combust in their solid state. Glass is an inorganic material with a very high melting point and does not burn. Concrete, being a composite of aggregates and cement, is also non-combustible as it does not ignite or support combustion. These characteristics set paper apart as a prime example of a combustible material.