虚拟语句问题

如果不是我同学们帮忙，我现在无法及时完成这个任务。
与现在事实相反，要用一般过去时。
所以选A。
could not不能表示与现在事实相反的情景。

谁告诉你不选B的？

你这几个选项里只能选B

but for + 名词短语-->含蓄地表示条件，是含蓄虚拟句，表示“若不是...”

如果表示对现在、将来虚拟，but for相当于If it were not for...
-----那么主句谓语形式就是：would(should, might, could) + do

如果表示对过去虚拟，but for相当于If it had not been for...
-----那么主句谓语形式就是：would(should, might, could) + have done

这句话最好的选择是:
But for my classmates' help, I wouldn't have finished the work in time.
因为没有 “would not have finished”这个选项
所以只能退而求其次，选择B“could not finish”
在这里But for my classmates' help=If it were not for my classmates' help，表示对现在或将来虚拟“要是没有同学们的帮助，我不可能及时完成任务”。

A. did not finish

应该选D,你可能写错了，应是would not have finished
因为对于过去的一种虚拟，属于含蓄条件句But for my classmates' help=If it had not been for my classmates' help

D. would not finished 对过去事情的假设.用would