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同学你好~
1. 在含系动词be、助动词be, have, has, will, would, shall, should等之后直接加not，构成否定句。如：
(1) He is there. — He is not there. 他不在那儿。

(2) I have finished my work. — I have not finished my work. 我的工作还没完成。

2. 否定含情态动词的句子：

a. 在情态动词can, could, may, might, must, need, dare, had better, would rather的句子之后直接加not。如：

(1) He can say so. — He can not say so. 它不会那样说。

(2) Students must smoke. — Students must not smoke. 学生不允许抽烟。

b. 在含情态动词ought to的句子，在ought to中的to前面加not，构成否定句。如：

(1) You ought to bother him. — You ought not to bother him. 你不应该去麻烦他。

(2) You ought to waste your time. — You ought not to waste your time. 你不应该把时间浪费了。

c. 在含情态动词used to的句子，可在used to中的to前面加not；也可在used前面加 did not，同时将used 改为use。如：

(1) He used to smoke in the past . — He used not to smoke in the past. 他过去不常抽烟。

(2) He used to live here. — He did not use to live here. 他原来常不住这里。

d. 在含情态动词have / has / had  to的句子，在have / has / had to前面加do not的适当形式, 同时将has / had 改为have。如：

(1) You do have to stay here after school. — You do not have to stay here after school. 你不必放学后还呆在这里。

(2) He had to go to work yesterday. — He did not have to go to work yesterday. 他昨天不必去上班。

3. 对于不含系动词be、助动词或情态动词的句子，则在谓语动词前加do not的适当形式, 同时将原谓语动词改为原形。如：

(1) He likes classic music. — He does not like classic music. 他不喜欢古典音乐。

(2) She played table tennis yesterday afternoon. — She did not play table tennis yesterday afternoon. 她昨天下午没有打乒乓球。




非谓语动词的否定式通常是将否定词not置于正个非谓语动词之前——如果非谓语动词为完成式，则应将否定词置于having或to have之前；如果非谓语动词为被动式，则应将否定词置于being或to be之前。如：　　

He pretended not to see me. 他假装没看见我。　　

You were lucky not to be killed. 你大难不死，真是好运气。　　

She’s angry about not having been invited. 她对没有受到邀请感到生气。　

当非谓语前带有逻辑主语时，否定句词习惯上是放在逻辑主语后，非谓语动词之前。如：　　

I’m surprised at your not having noticed. 你竟未注意到我感到吃惊。　　

In case of my not being here, ask my brother to help you. 如果我不在可让我弟弟帮助你。


祝同学学习进步~