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

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

2. 表示真理时，主句谓语动词不用shall (will) +动词原形，而直接用一般现在时的动词形式

1.真实条件句用于陈述语气，假设的情况有可能发生,各种结构如下：

条件从句　　　　　 主句

一般现在时　　 shall/will + 动词原形

祈使句　　　　 情态动词一般现在时

If he comes, he will bring his violin. 如果他来，会带小提琴来的。

[典型例题]The volleyball match will be put off if it___.

A.　will rain　　　 B. rains　　　 C. rained　　 D. is rained

[解析]B 真实条件句主句为将来时，从句用一般现在时。

[点拨]1. 在真实条件句中，主句不能用be going to表示将来，该用shall, will.

(错) If you leave now, you are never going to regret it.

(对) If you leave now, you will never regret it.