问题补充：
--Excuse me, I don think you can smoke here.
---Really sorry. I this is a non-smoking room.
A. didn know
B. don know
C. have no idea
D. haven known
答案：
(答案→)A. didn know
B. don know
C. have no idea
D. haven known
解析：考查时态：句子的意思是：——打扰一下，先生，这是禁烟室。——抱歉，我不知道这是禁烟室。“我不知道这是禁烟室”应该是发生在过去的事情，所以使用一般过去时即可。选A。
