摘要：need ⑴作为情态动词时主要用在否定句和疑问句中.但是也可以用在用条件的肯定句中.这个条件是:肯 定句中必须含有某些含某种否定含义的词语.例如only ,but ,all,before等或者说句子中暗含某 种否定含义. One need only consider the facts .否定含义是:只需考虑这些事实.不必去做别的事. He need do it but once .否定含义是:他不必做两次以上. All he need do is state his opinion clearly. 否定含义是:只要清楚地陈述自己的观点.他不必做任何事. 练习题: To become a member of the civic association ,one need only attend three meetings ,and his fees regularly. A. pay B.to pay C.paying D.paid ⑵didn't need to 和needn't have done 的区别: 前者表示没有必要做实际上也没有做某事.后者表示做了不该做的事情. They didn't need to come here.他们不必来这儿. They needn't have come here.他们本来不必来这儿 They did not need to arrive so early .他们不必很早到达. She was too nervous to reply ,but fortunately she did not need to say nothing . 她紧张的无法答话.但是幸运的是她什么也不需要说. You needn't have told them that .你本不必把这件事情告诉他们. 练习题: ①You such a long essay ,the teacher only asked for 300 words ,and you have written 600 words . A.mustn't have written B.needn't have written C.ddn't have to write D.didn'need to write ②You all those calculations !We have a computer to do that sort of thing. A.mustn{'t have done B.must not have done C.shouldn’t have done not have done

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