The correct answer is A. Kelvin.
Kelvin (K) is the SI unit of thermodynamic temperature. It is the base unit of temperature in the International System of Units (SI). It is named after the Scottish physicist and engineer William Thomson, 1st Baron Kelvin (1824â1907), who proposed it in 1848.
The Kelvin scale is an absolute scale of temperature, meaning that it is based on the laws of physics, rather than on any arbitrary reference point. The zero point on the Kelvin scale is absolute zero, the temperature at which all molecular motion ceases. The freezing point of water is 273.15 K, and the boiling point is 373.15 K.
Celsius (°C) and centigrade (°C) are two different names for the same temperature scale. The Celsius scale is a relative scale, meaning that it is based on two arbitrary reference points: the freezing point of water (0 °C) and the boiling point of water (100 °C). The Celsius scale is commonly used in everyday life, but it is not an SI unit.
Fahrenheit (°F) is a temperature scale that was developed by Daniel Gabriel Fahrenheit in 1724. The Fahrenheit scale is based on the freezing point of water (32 °F) and the boiling point of water (212 °F). The Fahrenheit scale is commonly used in the United States and a few other countries.