Explanation

Analysis of Each Statement:

Statement A: "is constant across exercise price and time to expiration"

• Least accurate - This is incorrect
• In reality, implied volatility varies significantly across:
  • Different exercise prices (volatility smile/skew)
  • Different time to expiration (volatility term structure)
• The Black-Scholes model assumes constant volatility, but real markets show volatility is not constant

Statement B: "may be used to revalue existing option positions over time"

• Accurate - Implied volatility can be used to mark-to-market option positions
• As market conditions change, implied volatility helps determine current option values

Statement C: "makes it easier to understand the current market price of various risk exposures"

• Accurate - Implied volatility represents the market's consensus on future volatility
• It helps traders understand the pricing of different risk exposures in the options market

Why Statement A is Least Accurate:

• Empirical evidence shows implied volatility is not constant
• Volatility smile: Different strike prices have different implied volatilities
• Volatility term structure: Different expiration dates have different implied volatilities
• This variation reflects market expectations about future price movements and risk

Correct Answer: A

Statement A is least accurate because implied volatility is not constant across exercise prices and time to expiration in practice.