From the list below, select the correct definition of inflation.
A. An increase in the level of output in an economy evidenced by a rising GDP.
B. A set of sustained increases in the price of a firm\'s stock.
C. A general and ongoing rise in the average level of prices in an economy.
D. A specific increase in the price of a good or service attributable to changes in supply or demand.
E. A general and ongoing rise in unemployment.
F. A general and ongoing decline in the level of prices in an economy.