What is $ 1000\;milligrams\,in\,kg? $
A. $ 0.1\;kg $
B. $ 0.01\;kg $
C. $ 0.001\;kg $
D. $ 0.0001\;kg $

Hint: The unit conversion depends on the situation or question. For example if the length of any thing is given in meters but we need to express the unit in centimeters or millimeters. Thus we need the unit conversion. There are many relationships to conversion.
As we know that
 $ 1\;kg = 1000\;g $

Complete step by step solution:
Given, $ 1000\;mg $
As we know that
 $ 1g = 1000\;mg $
So $ 1000mg $ will be
 $ = \dfrac{{1000}}{{1000}}\;g $
 $ = 1\;gram $
Now as we know that
 $ 1kg = 1000\;g $
So $ 1g\,in\,kg\,will\,be $
 $ = \dfrac{1}{{1000}}\;kg $
 $ = 0.001\;kg $
So the answer is (C) $ 0.001\;kg $ ,
So, the correct answer is “Option C”.

Note: Unit conversion is the process of converting one standard to another as per requirements. The need for the basic conversion is also exciting for different fields for different purposes. There are many online tools and software available for unit conversion. They work quickly and give accurate results.