单选题 I would have come sooner but I ______ that you were waiting.
A. didn't know B. haven't known
C. hadn't known D. hasn't known

【正确答案】 A

【答案解析】这是一个含蓄虚拟语气句，前半部分是假设的，而“不知道你在等待”却是真实情况。假设条件暗含在转折连词but中：If I had known that you were waiting, I would have come sooner,但事实是“I didn't know that you were waiting”。故A为正确答案。