The index number express-

The correct answer is: A. In percentage.

An index number is a statistical measure of changes in a variable over time. It is expressed as a percentage, with the base period being set equal to 100. For example, if the index number for consumer prices in 2023 is 120, this means that prices in 2023 are 20% higher than they were in the base period.

Option B is incorrect because index numbers are not expressed in rupees. Option C is incorrect because index numbers are not expressed in kilograms. Option D is incorrect because index numbers are expressed in percentage.