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