C is corrent. The requirement is to identify the formula for calculating a price index. The 2013 price index using 2008 as a reference period is the price of the 2013 market basket in 2013 relative to the price of the same basket of goods in 2008. The correct formula is
A is incorrect because the numerator and denominator are reversed.
B is incorrect because the 2008 market basket is used.
D is incorrect because it uses two different market baskets.
