without引导的虚拟语气!

1.与现在事实相反：
Without air,man couldn't exist on the earth.
没有空气的话,人类将不能在地球上生存.
谓语动词：would/could/might (not) do sth.
2.与过去事实相反：
Without your help,I would have failed the exam last week.
没有你帮助的话,我上周考试可能就通不过了.
谓语动词：would/could/might (not) have done sth.
3.与将来事实相反：
Without your ticket,I wouldn't be able to go to the concert tomorrow.
要是没有你的票的话,我明天就不能去听音乐会了.
谓语动词：would/could/might (not) do sth.