Which statement accurately reflects the behavior of flammable materials?

Flammable materials are substances that can easily ignite and burn when exposed to an appropriate source of ignition, such as a spark or a flame. This is due to their chemical composition and the presence of volatile compounds that vaporize and mix with air. The introduction of heat from a spark or flame provides the energy needed to initiate combustion, leading to a fire.

This behavior is not dependent on constant ignition, as flammable materials can continue to burn on their own once they are ignited, as long as they are provided with sufficient oxygen and fuel. Additionally, they do not require a vacuum environment to burn; in fact, most combustion occurs in the presence of air. Therefore, the correct statement highlights the necessity of an ignition source like a spark or flame to initiate the burning process of flammable materials.