21. Which of the following statements is true regarding volatility? a. an increase in implied volatility will make call values go up and put values go down since there is an increased probability of the underlying going up b. an increase in implied volatility will make call values go down and put values go up since there is an increased probability of the underlying going down c. a decrease in implied volatility will make call and put values go down because of the decreased probability of all strikes finishing in the money d. none of the above