A fire involving ordinary combustible materials such as wastepaper and rags would be classified as:

Fires involving ordinary combustible materials like wastepaper and rags are classified as Class A fires. This classification is specifically designated for fires that involve solid combustible materials, which are primarily organic in nature. Examples include wood, cloth, paper, rubber, and many types of plastics.

Class A fire extinguishing agents, such as water or foam, are effective in cooling the burning material and reducing temperatures to eliminate the fire's heat source. Understanding the classifications of fire is crucial for effective firefighting and safety planning, as it determines the appropriate extinguishing methods and agents to be used.

The other classifications pertain to different types of materials: Class B fires involve flammable liquids and gases; Class C fires involve electrical equipment; and Class D fires encompass combustible metals. Knowing the specifics of each class helps in selecting the right fire suppression techniques and ensuring safety during fire incidents.