初三英语语法习题,求解释_________ ,we could not have finished the work on time为什么选择 But for their help 不选was it not for their help 或者 should they offer to help

本题考查的是if对过去事实的虚拟，主句是could have done 时，if从句应该是had done, 二三两个答案时态搭配不对。

But for their help , we could not have finished the work on time.这是一个含虚拟语气的句子，后面部分的谓语 could not have finished 表示与过去事实相反的虚拟结果（事实上我们完成了），如果句子写完整，会是这样：If it had not been for their help ，we could not have finished the work on time. 这不是什么让步状语从句，在虚拟条件句中，它被称为“含蓄条件句”，这种语言现象你在今后的学习中会涉及到。另外 was it not for their help = If it was not for their help ，只能对现在情况进行假设，而 should they offer to help = If they should offer to help ，是对将来的假设，故不可用于此句。
希望你学有所成！

如果要用was it for their help ,就是用于现在相反的虚拟语态,但是给出的句子后半部分,不符合主句用would/ should/ could/ might +动词原形的形式,所以不是虚拟句.就应该用but for,做让步状语从句.如还有疑问,欢迎可...

天哪，初三就让做虚拟语气的题呀!!!
什么世道！！！
救救孩子！！！
was it not for their help 或者 should they offer to help都是时态不对的。