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But for(except, without) your help, I would have failed.

2)用其他方式代替条件状语从句(可以改写为条件状语从句)

①用动词不定式,例如：It would produce bad results to do that. =If you did that/should do that, it would produce bad results.

②用but,例如：She would have come, but she wasn’t informed, nor invited. =She would have come, if she had been informed or invited.

③用比较级,例如：A more responsible person would not have left the work half done. =If you (he, she) were more responsible, you (he, she) would not have left the work half done.

Chapter 5. 助动词

一、概念：

助动词是辅助主要动词构成各种时态,语态,语气以及否定或疑问结构的动词。助动词分为时态助动词和结构助动词两种,本身没有独立的词义,不能单独做谓语,在句子中只起语法作用,和实意动词一起构成谓语(叫复合谓语),表达否定,疑问,时态,语态和其他语法关系。其基本形式和作用如下表： 原形 现在式 过去式 过去分词 Be Am, is, Was, are were Been 现在分词 Being 构成各种进行时态和被动语态 作用

Have Has, have do Does, do Shall —— Had —— —— 构成各种完成时态 Did —— —— 构成疑问句和否定句、加强语气,代替前面相同的动词 Should —— —— 构成各种将来时态 二、相关知识点精讲： 1、助动词be的用法

1) be +现在分词,构成进行时态。例如：English is becoming more and more important. 英语现在越来越重要。

2) be +过去分词,构成被动语态。例如：He’s not respected by the press. 他们不受报界的尊重。

3) be +动词不定式,可表示下列内容：

a.表示最近、未来的计划或安排。例如：We are to teach the freshmen.我们要教新生。 说明： 这种用法也可以说成是一种将来时态表达法。

b.表示命令。例如：You are to explain this.对此你要做出解释。 c.征求意见。例如：How am I to answer him?我该怎样答复他?

d.表示相约、商定。例如：We are to meet at the school gate at seven tomorrow morning.我们明天早晨7点在校门口集合。 关于英语那些你不知道的事都在这里

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