问题
选择题
Never______ such a difficult problem. It took me almost half an hour to work it out.
A．had I come across
B．I had come across
C．did I come across
D．I did come across
答案
A
题目分析：考查倒装。句意：我从来没有见过这么难的问题，它花了我将近半个小时做出来。根据下文提到It took me almost half an hour to work it out 花费时间做出来发生在过去，所以我从来没有遇到，发生在过去的过去，用过去完成时， Never 不，放在句首，用部分倒装，所以选A项。
考点 : 考查倒装