A price index is:

a) a comparison of the current price of a market basket to a fixed point of reference.
b) a comparison of real GDP in one period relative to another.
c) the cost of a market basket of goods and services in a base period divided by the cost of the same market basket in another period.
d) a ratio of real GDP to nominal GDP.

a) a comparison of the current price of a market basket to a fixed point of reference.