What unit is used to measure absolute temperature?

The correct choice is based on the fact that absolute temperature is measured using scales that begin at absolute zero, the theoretical point where all molecular motion ceases. The Kelvin and Rankine scales are both considered absolute temperature scales.

The Kelvin scale is widely used in scientific contexts and is defined such that 0 K corresponds to absolute zero. Each increment on the Kelvin scale is equivalent to a degree Celsius, but with the zero point shifted. This allows for straightforward conversions between Celsius and Kelvin, which is essential when discussing gas laws, thermodynamics, and other physical principles inherent in fire science.

Rankine, while less commonly applied, serves a similar role in certain areas, particularly in thermodynamic calculations involving absolute temperatures in the Fahrenheit context.

In contrast, the Fahrenheit, Celsius, and Reaumur scales do not start from absolute zero and therefore cannot be considered absolute temperature scales. They measure temperatures relative to fixed points (like freezing and boiling points of water) without addressing the concept of absolute zero, making them unsuitable for this particular question.