The Implied Volatility of an Option

Multiple Choice

The implied volatility of an option

A) Is the volatility that would have to be plugged into a given option-pricing model to obtain the observed market price.
B) Can only be calculated using the Black-Scholes model.
C) Is the volatility implied by the underlying stock price over a given historical period.
D) Is equal to the volatility that will actually be realized over the life of the option.