A、  B、  C、  A以Why开头的问句是不会以Yes或No的形式来回答的。(B)就是由No开始的，所以不是正确答案。答案应该是(A)“我必须去看牙医”。

Would you like some help with dinner?
(A)No thanks, I’m almost done.
(B)Actually, I have plans tonight.
(C)Why don’t we try the Greek place?

Why weren’t you at the luncheon?
(A)I had to go to the dentist.
(B)No, I brought mine today.
(C)Sure, what day is good for you?