What type of materials would be classified as combustibles?

Combustibles are materials that can ignite and burn when exposed to a sufficient heat source. In the context of the question, drywall and wood are classified as combustibles because they are organic materials that contain cellulose and other compounds that readily catch fire. Wood, in particular, is well-known for its combustibility and is commonly used in construction, furniture, and various applications, while drywall can be flammable under certain conditions, especially when it's part of a composite structure (although it does contain fire-resistant chemicals.)

Other materials mentioned, such as brick and metal, glass and ceramic, and plaster on metal, are typically non-combustible or have fire-resistant properties. Brick is a solid, fire-resistant material, metal conducts heat but does not burn, glass is non-combustible and has a high melting point, and plaster on metal provides a fire-resistant barrier. Therefore, the focus on drywall and wood as combustibles makes option C the correct choice in this classification of materials.