if we() adequate preparations,the conference would not have been so successful

问题描述:

if we() adequate preparations,the conference would not have been so successful
为什么要填had not made?

had made
这是对过去的虚拟.条件从句必须使用过去完成时只要是对过去的虚拟,条件状语都必须用过去完成时?是的