What characterizes a flammable liquid?

The defining characteristic of a flammable liquid is its flash point, which is the lowest temperature at which the liquid can form an ignitable mixture with air. A liquid is classified as flammable if its flash point is not more than 70 degrees Fahrenheit (21 degrees Celsius). This means that at temperatures below or at this mark, the liquid can readily produce vapors that may ignite when exposed to an open flame or spark.

Understanding the flash point is crucial when handling, storing, and transporting liquids, as it directly relates to safety measures that must be taken to prevent fire hazards. Therefore, option C correctly identifies what makes a liquid flammable by focusing on the critical temperature threshold associated with ignition risk.