In the late $1990$s$,$ as information technology advanced rapidly and the Internet was widely developed, U$.$S$.$ stock markets soared, peaking in early $2001.$ Later that year, these markets began to unwind and then crashed, with many commentators identifying the previous few years as a "stock market bubble." Why was this episode considered a bubble?

A$.$ The growth rate of stock market prices increased by more than $25\%$ during this time.

B$.$ A higher number of risky but potentially profitable investments appeared.

C$.$ Stock market prices were overvalued and rose well above their fundamental values.

D$.$ Investors were able to exploit profit opportunities but only in the short term.