2. Johnny, you __ play with the knife. You ___ hurt youself.　

A. won't, can't 　　　 B. mustn't, may 　　 C. shouldn't, must 　　　　 D. cant't, shouldn't

1. Michael __ be a policeman,　 for he's much too short.

　A. need't 　　 B. can't 　 C. should 　　　 D. may

10．need用作情态动词，仅用于否定句和疑问句，而不用于肯定句。在肯定句中要用must, have to, should, ought to或将need当作行为动词使用。如：

We need report the matter to the boss immediately．(误)?

We must report the matter to the boss immediately．(正)

We need to report the matter to the boss immediately．(正)

情态动词表推测精炼精析

9．ought to与should意思接近，大多数情况下二者可以互换，但是should谈的是自己的主观看法，ought to则更多反映客观情况，在谈到法律、义务和规定时使用。如：

We should／ought to help each other and learn from each other in our work．

She is your mother, so you ought to support her．

We ought to go and see Mary tomorrow, but I don’t think we will．

8．should除表示必要或义务外，还可表示推测或可能。如：

The American friends should be here now．

“should／ought to+have+过去分词”既可表示本该做而事实上没有做的事，也可以表示惊讶、赞叹等情绪。如：You should have told her about it the day before yesterday．

It’s wonderful that you should have achieved so much in these years．

“情态动词+have+过去分词”是很重要的一种句型，除should外，may, might, must, couldn’t, needn’t, ought to等都可以用于这一句型，但要注意使用不同的情态动词,句子的意思就有所不同。

7．在表示将来的时间、条件状语从句中，不能用will(这时的will不是情态动词，而是助动词，帮助构成将来时)。如： If it will rain tomorrow, we shall not go to the mountain village．(误)?

If it rains tomorrow, we shall not go to the mountain village．(正)?

当情态动词will表示意愿或决心时，是可以用于条件状语从句的。如：

If you will listen to me, I’ll give you some advice on how to learn English．

如果你愿意听我的话，我将给你提点学习英语的建议。

If you will come this way, the manager will meet you． 请您往这边走，经理现在要见你。

6．shall可以用来征求对方意见。用于第一、三人称。此外它也可以用来表示说话人的命令、警告、允诺、威胁或决心等，这时它用于第二、三人称。如：

Shall she go to the concert with us this evening﹖ (征求意见)?

You shall go to the front at once．(命令)?

Don’t worry．You shall get the answer this very afternoon．(允诺)

He shall be sorry one day．I tell you．(警告)?

Nothing shall stop us from fighting against pollution．?(决心)?

5．must表示推测时，其反意问句有好几种形式。

1) “must+动词原形”对目前的情况进行推测时以及用must+be+-ing形式对目前正在发生的情况进行推测时，疑问短语部分要与must之后的动词相一致。如：

The mathematics teacher must be in the office now, isn’t he﹖

2) “must+have+过去分词”用来表示对已经发生的事情进行推论。如果句子中有过去的时间状语，疑问部分用助动词didn’t?否则，疑问部分用haven’t或hasn’t。如：

The children must have watered the tomatoes yesterday, didn’t they﹖

The minister must have arrived in Shanghai, hasn’t he﹖

4．must与have to都可以表示“必须”的意思，但要注意以下两点区别。

1) must只有现在时，而have to有现在时、过去时和将来时。如：

We must work hard, or we’ll fail in the examination．

Two years ago, the poor girl had to leave school for lack of money．

2) must表示主观看法，have to则侧重于客观需要。如：

We must be strict with ourselves in everything．

In cities with many cars, some people have to wear masks．

3．在过去时态的肯定句中需要某种条件或努力做成某事，我们要用was/were able to而不能用could。如：

It was a holiday and the children were able to go to the seaside．

The girl worked hard so she was able to pass the final test．