文档介绍：今天我们要来复****的是专业四级语法：have to, have got to, must not, need
在现代英语中，have to中不定式和疑问句式既可以按照助动词的变化规则构成，也可以 按照行为动词的变化规则构成。
Have you to finish the work before supper?
Do you have to finish the work before supper?
have got to常可同have to换用，但有时表示不同的含义。比较：
He has to report to the headquarters every two days.（例行公事****惯动作）
He has got to report to the headquarters every two days.（一道指示或命令，必得 每天报告一次）
另外，作“有”解时，have got和have通常是可以换用的，have got更口语化，但有时 表示不同的含义。比较：
The man has a blind 。
The man has got a blue 。
must not表示禁止，是说话人强有力的劝告或命令，意为“一定要，不准”。因此，在回答 由must引导的问题时，如果是否定的回答，表示“不必，没有必要”，不能用mustn't,而要用 needn't don't have ：
You must not drive 。（路险或有速度限制）
You needn't drive fast.（时间充裕）
You must not tell others.（警告）
You needn't tell others.（没有必要）
needs 为畐U词， 相当于 necessarily, of necessity, must needs 和 needs must 均可表 示“必须，必定，不得不”，这层意义上可以通用；但must needs还可表示“偏偏，偏要”，含 有讥讽、不满的意思，而needs must则一般无这层意思。例如：
I must needs go there now.
我现在非到那里去不可。（可用needs must）
Needs must when the devil drives.
情势所迫不得不那样。
She must needs go away when I want her.
我正需要她时，她偏偏离开了。（不可用needs must）
The telephone must needs ring when I went to bed.
我上床睡觉时偏偏有人来电话。（不可用needs must）
need指主语的主观特需情况而使之必要。need既可以作助动词，又可以作行为动词。作 助动词时，need没有人称和数的变化，后接不带to的不定式（动词原形），否定式为needn't. 作行动动词时，need同别的行为动词一样，有人称和数的变化，后接带to的不定式，否定式 要在前面加don't （doesn't, didn't）,疑问句用do （does, did）提问。例如：
There need be no hurry, need there?
He need never know. （= He never needs to know.）
I need only add a few words. （= I only need to add a few words.）
比较：
Father sent me the book, so I didn't need to write to him for it.
父亲把那本书寄来了，所以我不必为此给他写信了。（信没写）
Father sent me the book, so I need n't have written to him for it.
父亲把那本书寄来了，所以我本不该为此再写信给他的。（信已写）
She didn't need to 。（实际也没来）
She needn't have 。（但却来了）
Note:
，在肯定句中常用must, have to, should, ought to等。例如：
Need you do it right now? I need n't, but he must.
She does n't need to be told. She has already known it.