【题目】If we _______ adequate preparations, the conference wouldn't have been so successful.
A.haven't made
B.wouldn't make
C.didn't make
D.hadn't made

【答案】D
【解析】句意：如果我们没有做好充分的准备，会议就不会这样成功。在虚拟条件句中，表示与过去事实相反的情况，从句用过去完成时，主句用would have done的形式。故选D。