The Wilshire 5000 Stock Index Is

The Wilshire 5000 stock index is

A) an index of the 2000 largest industrial companies whose shares trade in U.S.markets.
B) an index of all the companies with U.S.headquarters whose shares trade in the U.S.
C) an index of 5000 major companies whose shares trade in U.S.markets.
D) an index of the average stock prices of many small firms operating in the U.S.