What is the flashpoint of flammable liquids?

The correct answer identifies the flashpoint of flammable liquids as the lowest temperature at which they can vaporize to form an ignitable mixture with air. This means at this critical temperature, enough vapor is produced by the liquid that it can mix with the air in a way that will support combustion. Understanding the flashpoint is essential for fire safety, especially in torch operations where such liquids are often used.

This characteristic helps in assessing the risk of fire involved with handling, storing, or using flammable liquids. Knowledge of the flashpoint informs safety protocols and the safe operating procedures in environments where flammable substances are present.

The other options do not accurately define flashpoint. The highest temperature at which a liquid can ignite is not a correct descriptor of flashpoint, as it does not reflect the minimum condition needed for vapor formation. Defining it as the temperature at which a liquid becomes non-flammable or the temperature necessary to extinguish a fire is misleading, as these concepts refer to different parameters of flammability and combustion, unrelated to the actual flashpoint definition.