What symbolizes that a fire extinguisher is suitable for use on ordinary combustibles?

The correct indication that a fire extinguisher is suitable for use on ordinary combustibles, such as wood, paper, and cloth, is represented by a red triangle. This symbol is part of a standardized system that helps users quickly identify the appropriate type of extinguisher for specific fire classes. The red triangle specifically signifies class A fires, thus guiding users in emergency situations to select the right extinguisher for their needs.

This classification system is vital for safety, as using an inappropriate type of extinguisher can be ineffective or even exacerbate the fire situation. The other options, while they might represent different classifications of fire extinguishers or other safety symbols, do not relate to the suitability for ordinary combustibles. Therefore, understanding the significance of the red triangle is essential for effective fire safety practices.