X is the measure and adjustment of price levels for goods and services across a broad sector of the economy, where X is:

Correct option is B

Indexation: Indexation is the process or technique through which the Government or Organization adjusts the purchase price of an asset to account for inflation between the time you bought and sold it.
it can be done to adjust for the effects of inflation, cost of living, or input prices over time, or for different prices and costs in different geographic regions.