The correct answer is (a) Population.
The Fourteenth Finance Commission of India was constituted on 29 January 2013 by the President of India, Pranab Mukherjee, to recommend the devolution of central taxes and duties to the states for the period 2015-2020. The Commission submitted its report on 16 December 2014.
The Commission assigned 7.5 percent weight to population as a criterion for tax sharing with the states. This is in line with the recommendations of the previous Finance Commissions. The Commission noted that population is a good indicator of the needs of the states and that it is a fair and equitable basis for devolution of resources.
The other options are not correct.
(b) Demographic change is not a criterion for tax sharing with the states. The Commission noted that demographic change is a complex issue and that it is difficult to quantify its impact on the needs of the states.
(c) Area is not a criterion for tax sharing with the states. The Commission noted that area is not a good indicator of the needs of the states.
(d) Forest cover is not a criterion for tax sharing with the states. The Commission noted that forest cover is not a good indicator of the needs of the states.