单项选择题

Customer: Excuse me!Clerk: Yes, ma-am What can I do for youCustomer: I have a problem with this coffee maker, and I want my money back.Clerk: ______ Customer: The problem is that it doesn't work! I've only used it three times.

A.Why
B.Well, are you sure
C.What's the matter with it on earth
D.Well, what seems to be the problem