Name the temperature scale used in the S.I. system.
(A) Kelvin scale
(B) Celsius scale
(C) Fahrenheit scale
(D) All of the above

Hint: We will take into account the most basic scale out of the four. Then finally we will choose an answer out of them.

 Step By Step Solution
All of the three are scales used to measure temperature.
But, out of the three only Celsius and the Fahrenheit scale are found in practical life.
The Kelvin scale is a standardized theoretical scale.
Now,
The question comes that how to relate all the scales,
There is a universal formula for this problem.
And the formula is given by:
\[\frac{{{T_{new}} - {L_{new}}}}{{{U_{new}} - {L_{new}}}} = \frac{{{T_{old}} - {L_{old}}}}{{{U_{old}} - {L_{old}}}}\]
Here,
Now,
For,
Celsius scale, \[L = {0^0}C\] and\[U = {100^0}C\].
And for Fahrenheit scale,
\[L = {32^0}F\] and \[U = {212^0}F\]
Now,
Let us say if we are given to convert \[{10^0}C\] to Fahrenheit, we will use the formula as
\[\frac{{{T_{new}} - 32}}{{180}} = \frac{{10 - 0}}{{100}}\]
Thus, we get
\[{10^0}C = {50^0}F\]
But,
For conversion to kelvin, we have to bring the temperature first to the Celsius scale and the apply the following relation
\[K{ = ^0}C + 273.16\]
Hence, the scale used for temperature in S.I. units is (A) Kelvin scale.

 Additional Information The value \[0K\] is referred to as absolute zero temperature. This means the value is \[0K\] or \[ - {273.16^0}C\] or\[ - {459.67^0}F\].

 Note: We took the kelvin as the standard as it is the only non-practical unit and also the other units could be converted to it. In other words we fix the origin of temperature fluctuation as on the Kelvin scale.
Thus, it is a good practice to convert any given temperature to Kelvin and then proceed with further manipulations.