The SI unit of temperature as per the International System of Units is Kelvin. This is because Kelvin is an absolute temperature scale, which means that 0 K is the lowest possible temperature that can be reached, also known as absolute zero.

Explanation:
1. SI Unit of Temperature:
The International System of Units (SI) is a modern form of the metric system that is the world's most widely used measurement system. It defines seven base units of measurement, which includes the unit of temperature.

2. Kelvin Scale:
The Kelvin scale is an absolute temperature scale that is based on the theoretical concept of absolute zero, which is the point at which all matter stops moving. The scale is named after the British physicist William Thomson, also known as Lord Kelvin.

3. Why Kelvin is the SI Unit of Temperature:
The Kelvin scale is the SI unit of temperature because it is an absolute scale that is based on the fundamental properties of matter. Unlike the Celsius and Fahrenheit scales, which are relative scales, the Kelvin scale is an absolute scale that is universally accepted.

4. Relationship between Celsius and Kelvin:
The Celsius scale is based on the freezing and boiling points of water under standard conditions, while the Kelvin scale is based on absolute zero. The relationship between Celsius and Kelvin is given by the equation K = °C + 273.15, where K is the temperature in Kelvin and °C is the temperature in Celsius.

In conclusion, the SI unit of temperature is Kelvin because it is an absolute temperature scale that is universally accepted and based on the fundamental properties of matter.

Option C is correct. The quantity of Kelvin is Thermodynamic temperature