初三英语语法习题，求解释_________ , we could not have finished the work on time

Question

为什么选择 But for their help ？不选was it not for their help 或者 should they offer to help

Answer 1

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！

Answer 2

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。

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Answer 3

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。

Answer 4

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。