Which of the following describes (auto) ignition temperature?

Correct Answer: Option D — the temperature at which no spark or flame is required to ignite gas or vapor

Auto-ignition temperature is the minimum temperature required to initiate self-sustained combustion in a substance without the presence of an external ignition source like a spark or flame. This property is critical for assessing fire hazards, as materials can ignite simply by contacting a sufficiently hot surface or environment.