1．He may /might be very busy now.
2．Your mother may /might not know the truth.
三、 must, have to
1) 表示必须、必要。
You must come in time.
在回答引出的问句时，如果是否定的，不能用mustn’t（禁止，不准），而用needn’t, don’t have to（不必）.
---- Must we hand in our exercise books today?
---- Yes, you must.
---- No, you don’t have to / you needn’t.
2) must是说话人的主观看法， 而have to则强调客观需要。Must只有一般现在时， have to 有更多的时态形式。
1． he play isn’t interesting, I really must go now.
2． I had to work when I was your age.
3) 表示推测、可能性（只用于肯定的陈述句）
1． You’re Tom’s good friend, so you must know what he likes best.
2． Your mother must be waiting for you now.
四、 dare, need
1) dare作情态动词用时, 常用于疑问句、否定句和条件从句中, 过去式形式为dared。
1． How dare you say I’m unfair?
2． He daren’t speak English before such a crowd, dare he?
3． If we dared not go there that day， we couldn’t get the beautiful flowers.
2) need 作情态动词用时, 常用于疑问句、否定句。在肯定句中一般用must, have to, ought to, should代替。
1．You needn’t come so early.
2. ---- Need I finish the work today?
---- Yes, you must. / No, you needn’t.
3) dare和 need作实义动词用时， 有人称、时态和数的变化。在肯定句中，dare后面常接带to的不定式。在疑问句和否定句中，dare后面可接带to或不带to的不定式。而need后面只能接带to的不定式。
1. I dare to swim across this river.
2. He doesn’t dare (to) answer.
3. He needs to finish his homework today.
五、 shall, should
1) shall 用于第一人称，征求对方的意见。
What shall we do this evening?
2) shall 用于第二、三人称，表示说话人给对方的命令、警告、允诺或威胁。
1. You shall fail if you don’t work hard.(警告)
2. He shall have the book when I finish it.(允诺)
3. He shall be punished.(威胁)
六、 will, would
1) 表示请求、建议等，would更委婉。
Will / Would you pass me the ball, please?
2) 表示意志、愿望和决心。
1. I will never do that again.
2. They asked him if he would go abroad.
3) would表示过去反复发生的动作或某种倾向。would表示过去习惯时比used to正式，且没有“现已无此习惯”的含义。
1. During the vacation, he would visit me every other day.
2. The wound would not heal.
4) 表示估计和猜想。
It would be about ten o’clock when she left home.
七、 should, ought to
1) should, ought to表示“应该”，ought to表示义务或责任，比should语气重。
1. I should help her because she is in trouble.
2. You ought to take care of the baby.
2) 表示劝告、建议和命令。should, ought to可通用，但在疑问句中常用should。
1. You should / ought to go to class right away.
2. Should I open the window?
3) 表示推测
should , ought to (客观推测), must(主观推测)。
1.He must be home by now. (断定他已到家)
2.He ought to/should be home by now.(不太肯定)
3. This is where the oil must be.(直爽)
4. This is where the oil ought to/should be.(含蓄)
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回答者： shendahai -
prefer最常见的意思是\宁可\、\宁愿(选择)\、\比较喜欢\、\更喜欢\等, 可以构成以下结构。
一. prefer sth.
\你喜欢法语吗?\喜欢,但是我更喜欢英语。\
注:prefer是\比较喜欢,更喜欢\的意思,即like better,因此就不能再与better, more等比较级词语连用。
二.prefer over sth.
I prefer over this newly-built lab, and you? 我比较喜欢这个新建的实验室,你呢?
They prefer over new works that sing of their life today. 他们更喜欢歌颂他们今天生活的新作品。
三. prefer sth. above all others
I prefer the book above all others. 我最喜欢这本书。
四. prefer A to B
I prefer the original book to the revised edition. 我觉得原书比修订本好。
五. prefer doing A to doing B
Even on holidays Mr. Wang preferred reading to doing nothing. 即使在假日,王先生宁愿读书而不愿闲着。
注:在这种结构中,to为介词,而不是不定式符号,故其后应当接动名词形式,决不能接动词原形。另外,为了保持前后对应关系,prefer后面也应当接动名词形式。
六. prefer to do sth.
They prefer to spend the rest of the morning wandering in the streets. 他们比较喜欢把早上剩下的时间都用来在街上闲逛。
七. prefer doing sth.
So you prefer speaking without referring to your notes? 这么说,你更喜欢不看稿子做报告了?
注: 这种prefer后面接动名词的结构,用来谈论一般情况下\更喜欢某种活动\而在一个特定场合下表示\特别喜欢\时,得用上述prefer后接动词不定式结构。
八. prefer to do sth. rather than do sth.
These workers prefered to work extra hours at night rather than leave the work until the next week. 这些工人宁愿加班干,也不愿把工作留到下一个星期。
注:这种结构中的rather than可以置于句首。例如:
Rather than go on holiday to the seaside I prefer to work days and go to school nights. 我宁愿白天工作,晚上上学,而不愿到海边度假。
注:有时rather可以移至第一个不定式之前,而让than留在第二个不定式之前,即为prefer rather...than结构.这种用法多见于书面语言,在口语中很少用.
九. prefer to do sth. rather than doing sth.
They prefer to join in the celebrations rather than going on a visit to the Palace Museum. 他们宁愿参加庆祝活动而不愿参观故宫。
注:有时名词也可用于rather than之后,这种用法多用以表示在某种具体场合的选择。 十. prefer sb. to do sth.
I prefer you to spare some time to come to our art exhibition next week. 我宁愿你们下星期抽出点时间来看看我们的美展。
十一. prefer+that-clause.在that宾语从句中,我们应当用虚拟语气\动词原形\其中的should可以省略。
which的用法
