The correct answer is option 'C' - 2011-12.

Explanation:

The Wholesale Price Index (WPI) is an important indicator used to measure the average change in the prices of goods at the wholesale level in a given period of time. It is published by the Office of the Economic Adviser, Ministry of Commerce and Industry, Government of India.

The WPI is calculated using a fixed base year method, where a specific year is chosen as the reference year against which the price changes are measured. The base year serves as a benchmark for comparison and provides a reference point for calculating the index.

The base year used for the WPI has undergone multiple revisions over the years to account for changes in the economic scenario and price movements. The most recent revision was made in 2011-12.

During the revision process, a new set of representative commodities and weights are selected based on their significance in the economy. These commodities are chosen from various sectors such as agriculture, manufacturing, mining, and electricity.

The base year is chosen to reflect a period of relative stability and representative of the economic structure. It should be a year when the economy is considered to be in a normal state, without any major fluctuations or disruptions.

The choice of the base year is crucial as it affects the calculation of the index and the interpretation of the results. The base year should be periodically revised to ensure that the WPI remains accurate and relevant in reflecting the changes in the economy.

In the case of the WPI, the base year used is 2011-12. This means that the price movements of various goods are measured relative to the prices prevailing in 2011-12. The weights assigned to different commodities are also based on their importance in the 2011-12 economy.

By using a fixed base year like 2011-12, the WPI provides a useful tool for monitoring and analyzing inflationary trends in the economy. It helps policymakers, economists, and businesses to understand the price dynamics and make informed decisions based on the changes in wholesale prices.

In conclusion, the correct base year used for the WPI is 2011-12.