单选题 Kevin: Is this Mr. Graber's office?
Receptionist: Yes, that's right. ______
Kevin: I'd like to see Mr. Graber, but I haven't got an appointment, I'm afraid.
Receptionist: I'm sorry but Mr. Graber is engaged at present.

• A. What do you want?
• B. Are you looking for him?
• C. Can I be of any assistance?
• D. Good mornin