A Recent Monthly Press Release on the Consumer Price Index

Multiple Choice

A recent monthly press release on the Consumer Price Index says: "The Consumer Price Index for All Urban Consumers (CPI-U) dropped 0.1 percent in August, before seasonal adjustment, to a level of 218.8 (1982-84 = 100) , the Bureau of Labor Statistics of the U.S. Department of Labor reported today."
What does "1982-84 = 100" mean here?

A) The CPI did not exist before 1982.
B) The CPI increased by 100 between 1982 and 1984.
C) The CPI measures prices relative to what they were in the years 1982 to 1984.
D) To find the CPI, start with 1982-84 prices and add 100.