Which of the following is true? When the volatility decreases,

	A.	the values of both calls and puts decrease.
	B.	the values of American calls and puts increase, but the relationship between volatility and the prices of European options is uncertain.
	C.	the value of a call option decreases, whereas the value of a put option increases.
	D.	the value of a call option increases, whereas the value of a put option decreases.