Which of the following is considered an ordinary combustible material?

Ordinary combustible materials are those that can ignite and burn easily, characterized primarily by their organic composition. Wood and paper fall into this category as they are widely known for their combustibility under appropriate conditions. Both materials are composed of cellulose and other organic compounds, making them susceptible to ignition when exposed to heat or flames.

In addition, ordinary combustibles are often found in everyday environments, such as homes and workplaces, and they can generate substantial amounts of heat and smoke when they burn, which is crucial information for fire safety and firefighting strategies.

The other choices, while flammable or combustible, belong to different classifications of materials. Gasoline and alcohol are classified as flammable liquids, which have lower ignition points and burn more rapidly than ordinary combustibles. Cooking oil may also pose a hazard as it can ignite at high temperatures and is often categorized with flammable liquids in terms of fire behavior.