4.　通过分词短语表示条件

Given more time, we could have done it better.

Legalizing this drug would have disastrous consequence . 使毒品合法化会有灾难性的后果

3.　连词otherwise, or, but

He would have given you more help , but he has been so busy . 他本来要多给你一些帮助，只是他太忙了

Seize the chance , otherwise you would regret it . 如果不抓住这个机会，你会后悔的

He felt very tired yesterday , or he would have helped you . 他昨天觉得很累，不然会帮你的

2.　介词及介词短语but that, as though, once , but for, without , with , under , under…condition , supposing , suppose , as if , on condition that , in the past 等

But for his pension , he would starve .要不是有养老金，他都要饿死了

Without your help , I couldn’t have achieved all this . 要不是有你帮助我不会取得这些成就

With his aid , you would succeed . 如果有了他的帮助，你就会成功。

Plants would die without water on the earth . 地球上如果没有水，植物就会死的

But for the fog we would have reached our destination long ago . 要是没有雾的话，我们很早就到目的地了

Under more favourable conditions we could have finished the task . 如果条件对我们更有利，我们就会把工作完成得更好

1.　定语从句和状语从句

Anyone who had married such a girl as she would have been regretful . 谁娶了像她这样的姑娘都会后悔的

help was promised where it should become necessary . 要是需要的话就答应给予帮助

4.　If the doctor had come in time , any would still be alive . 如果医生及时赶到，AMY现在还活着。

3.　If it hadn’t been for her care , I should not be speaking to you now. 如果不是她照顾我，我也不会在这里和你讲话

2.　If you’d listened to me , you wouldn’t be in such trouble now . 如果你听了我的话，你现在也不会这样麻烦了

有时，主句与从句的动作发生在不同的时间，主句从句谓语动词的虚拟语气形式因时间不同而不同，这种条件句叫做混合条件句

If you had asked him yesterday, you would know what to do now. 如果你昨天问过他，今天就知道做什么了。(从句与过去事实相反，主句与现在事实相反。)

1.　If it had rained last night(过去), it would be very cold today (现在).如果昨晚下过雨，今天就会很冷了。

2.　虚拟语气表

时间	从句	主句	例句
与现在事实相反的假设	一般过去时( be 用were)	Would / should / could / might / ought to　 + 动词原形	1.　If they were here, they would help you. 2.　If we had enough money , we would buy a computer . 3.　If I were you , I wouldn’t do it . 4.　If it rained tomorrow , we’d stay at home . 5.　It would be odd if she were awarded the first prize .
与过去事实相反的假设	过去完成时	Should / would / could / might + have+ 过去分词	1.　If he had come yesterday, I should have told him about it. 2.If I had been in her position I’d have quit . 3.　If the weather hadn’t been so bad , we might have gone out . 4.　If he had apologized , you should have done so too. 5.　I should never have done it if I hadn’t been so hard up .
与将来不大可能发生的事情的假想	一般过去时 / should/would 　 + 动词原形	Should / would　 / could / might / ought to + 动词原形	1.　If you succeeded, everything would be all right. 2.　If they invited me , I would certainly attend it . 3.　If he went , would you go too ?
与将来事实相反的假设	were+ 不定式	Should / would　 / could / might / ought to + 动词原形	1.　If she were to lose her place they would be ruined . 2.If you were to speak to him , it would carry more weight .

1.　虚拟语气可以表示过去，现在和将来的情况，时态的基本特点是时态往后推移