The kelvin is the primary unit of temperature measurement in the physical sciences, but is often used in conjunction with the Celsius degree, which has the same magnitude. The definition implies that absolute zero (0 K) is equivalent to −273.15 C (−459.67 F). 

The correct answer should be C.The SI unit of temperature as per the International System of Units is Kelvin which is represented by the symbol K. However, in most parts of the world, Celsius or Fahrenheit scale is used for measuring temperature.While Kelvin is used mainly in scientific applications, celsius is used in day to day applications. The same sentence is also mentioned in Geography NCERT of Class VII. Refer to the Chapter Air.

The standard unit of measuring temperature is Celsius. It is named after the Swedish astronomer Anders Celsius who first proposed a similar system in 1742.

Importance of measuring temperature
Temperature is an important physical quantity that is measured in many scientific and industrial processes. It is a measure of the average kinetic energy of the particles in a substance, which determines its physical properties and behavior.

Units of temperature
There are several units of temperature that are used around the world, including Fahrenheit, Celsius, and Kelvin. However, Celsius is the standard unit of temperature in the International System of Units (SI).

Advantages of Celsius
Celsius is preferred over other units of temperature for several reasons:

1. It is based on the metric system, which makes it easier to use for scientific measurements and calculations.

2. It has a simple and intuitive scale, where 0°C represents the freezing point of water and 100°C represents the boiling point of water at sea level.

3. It is widely used and recognized around the world, making it easier to communicate temperature measurements across different languages and cultures.

Conclusion
In conclusion, Celsius is the standard unit of measuring temperature because it is based on the metric system, has a simple and intuitive scale, and is widely used and recognized around the world.