Debbie has two stocks, X and Y. Consider the following events:

X = the event that the price of stock X has increased
Y = the event that the price of stock Y has increased

The event "the price of stock X has increased and the price of stock Y has not increased" may be written as

(A) X′ ∩ Y
(B) X or Y′
(C) X or Y
(D) X ∩ Y′