Which of the following is NOT a material that a Class A fire extinguisher is effective against?

A Class A fire extinguisher is designed specifically to combat fires involving ordinary combustible materials. These materials include wood, paper, cloth, plastics, rubber, and other similar substances. The effectiveness of a Class A extinguisher is primarily due to its capability to cool and extinguish these types of fires.

On the other hand, gasoline is classified as a Class B fire hazard. Class B fire extinguishers are intended for use on flammable liquids like gasoline, oil, and grease. Therefore, while a Class A extinguisher is effective against materials like wood, plastics, and rubber, it is not effective against gasoline fires, making this the correct answer.

Understanding the classification of fires and the corresponding types of extinguishers is crucial for effective fire management and safety.