问题补充：
Hardly the door when he rushed into the office out of breath.
A. I opened
B. did I open
C. I had opened
D. had I opened
答案：
A. I opened
B. did I open
C. I had opened
(答案→)D. had I opened
解析：hardly 以及含有否定意义的副词放在句首，句子用倒装结构。
hardly…when/ no sooner…than 用法相同。
