Which of the following labels indicates that a substance is flammable?

The label that indicates a substance is flammable is "Flammable Liquid." This label is specifically designed to identify substances that can easily ignite and sustain combustion. Flammable liquids have a flash point below a certain temperature, indicating that they can produce enough vapor to form an explosive mixture with air. Understanding the hazards associated with flammable substances is crucial for safe handling, transportation, and storage in order to prevent fires and explosions.

The other labels refer to different types of hazards. An "Explosive" label indicates materials that can rapidly decompose, producing gas and heat, potentially resulting in an explosion. A "Corrosive" label signifies materials that can cause destruction to living tissue or severe corrosion of materials. Lastly, a "Non-flammable Gas" label is used for gases that do not ignite and therefore do not present a fire risk. Only "Flammable Liquid" directly points to a fire hazard related to combustion, making it the correct answer for identifying flammable substances.