The Reason Why Many Economists Switched from Using M1 to M2

The reason why many economists switched from using M1 to M2 as the best measure of the medium of exchange is that

A) during the 1980s, new substitutes for checking accounts appeared and were included in M2.
B) during the 1980s, the country went off the gold standard and began using fiat money for the first time.
C) during the 1980s, inflation roared out of control and a better measure of the money supply seemed necessary.
D) in 1982, the federal government ordered that all income taxes must be paid using M2.