Correct Answer - Option 2 : It is used for the base of planned economy.
Index number is a number used to measure the level of certain phenomena as compared to the level of the same phenomenon
We also defined as the index number is used to for comaring between the price, quantity etc
We can take an example to understand index number at a certain place or a period of time and that of another place or period of time
Basically Index number are used for the base of planned economy
∴ Option second is correct answer