—Did you forget about my birthday?-- I’ve booked a table for this evening.A. What then?B.

问题补充：

—Did you forget about my birthday?

-- I’ve booked a table for this evening.

A. What then?

B. I’m afraid so.

C. How could I ?

D. For sure.

答案：

A. What then?

B. I’m afraid so.

(答案→)C. How could I ?

D. For sure.

解析：what then？接下来怎么办？那便会怎么样？I am afraid so恐怕是这样的；How could I ? 怎么可能？For sure确信；句义：—你忘记我的生日了吗？—怎么可能？今天晚上我已经订了一个桌子一起吃饭了。根据句义说明表示的是疑问。故C项符合上下文含义。