Question

Why is the S.I unit defined by the general conference of weight and measure?

Answer 1

Hint : In order to answer the question, we will discuss the 11th general conference on weights and measures in which it was redefined the S.I unit and we will also discuss why the S.I unit is defined by the general conference of weight and measures.

Complete Step By Step Answer:
Adopted by the 11th General Conference on Weights and Measures (CGPM) in 1960, it is abbreviated SI in all languages.
After long conversation the eleventh General Conference on Weights and Measures (eleventh CGPM), meeting in Paris in October 1960, planned another International System of Units (condensed SI). The SI was corrected by ensuring meetings of the CGPM. The accompanying base units have been adopted and characterized.
The General Conference on Weights and Measures (CGPM), with political delegates of somewhere in the range of 40 nations, meets at regular intervals to think about change. The gathering chooses 18 researchers who structure the International Committee for Weights and Measures that administers the agency.
In this general conference, it redefined many units such that:
(i). Ampere: In 2018 the General Conference on Weights and Measures (CGPM) agreed that on May 20, 2019, the ampere would henceforth be defined such that the elementary charge would be equal to $1.602176634 \times {10^{ - 19}}\;coulomb$ .
(ii.) Kelvin: The 2018 General Conference on Weights and Measures concluded that compelling from May 20, 2019, the unit would be characterized with the end goal that the Boltzmann steady would be equivalent to $1.380649 \times {10^{ - 23}}joule{\text{ }}per{\text{ }}kelvin$ .
(iii). Kilogram: with an evolving mass, the General Conference on Weights and Measures (CGPM) concurred in 2011 to a proposition to start to rethink the kilogram not by an actual antiquity but rather by a key actual steady.
(iv). Mole: The General Conference on Weights and Measures characterized the mole as this number for the International System of Units (SI) compelling from May 20, 2019. The mole was recently characterized as the quantity of molecules decided tentatively to be found in 12 grams of $carbon - 12$ .

Note :
The SI base units and their physical quantities are the metre for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the candela for luminous intensity, and the mole for amount of substance.