What are the characteristics of flammable liquids based on flash point?

Flammable liquids are classified based on their flash points, which is the lowest temperature at which the vapors of a liquid can ignite in air. The correct choice states that liquids with a flash point below 100°F (37.8°C) are considered flammable. This definition aligns with established safety standards and regulations that categorize flammable liquids based on their ability to form ignitable mixtures with air at relatively low temperatures.

Liquids with flash points below this threshold pose a significant risk of fire under ambient conditions, making them hazardous materials that require careful handling and storage.

In contrast, other options describe characteristics that do not accurately represent flammable liquids. For instance, spontaneous ignition at room temperature is characteristic of a different category of substances, often classified as pyrophoric materials rather than flammable liquids. Flash points above 200°F categorize liquids as non-flammable, and substances that react violently with water likely pertain to corrosive or reactive materials, which do not fit the definition of flammable liquids at all.