情态动词专题情态动词表示说话人的语气和态度.如需要、同意和怀疑等。它们有一定的词义，但不完整，必须和主要动词的原形一起构成谓语，常用的情态动词有： can, could， may， might， must， have to， ought to， should， will， would， need， dare, shall， ， be able to 及半情态动词 had better， would rather， have to, would like to。情态动词的基本用法：一、can 1. 表示能力“能……， 会……”A computer can’t think for itself； it must be told what to do.2。 表示许可,“能够……， 可以……”；在疑问句中表示请求许可“能不能……，要不要……,用 could 表委婉语气,还可以用 may。You can go out to play when you finish your homework. —-Can /Could /May I go now ?—Yes， you can/may。 Could you give me a lift to the station?3. 表示猜想,通常用在疑问句中，表示惊讶、怀疑;用于否定句中,表示有把握的否定推测“不可能……”Who can it be ？那会是谁呢？ Can it be true？ 那会是真的吗?She can’t be waiting for you。 她不可能在等你.He can’t have gone there alone.他不可能独自一人到那儿去。4。（表示平常大部分时间不是这样,只是偶然发生）“有时候会……”。Someequipment at home can be dangerous to children。 Peter can be really hard to get along with even though he is a nice person in general。特别记忆：① can not/ can never…too… 或 cannot … enough“再……也过分，越……就越好"You can never be too careful （you can’t be careful enough ）while crossing the street. ②can't help doing sth。= can't help but do sth = can't but do sth =can do nothing but do sth.When a close friend dies， you can’t but feel sad。③were /was able to do sth。 表示过去设法成功地做了某事，could 没有此意The fire spread through the hotel very quickly， but everyone was able to get out.④can’t/couldn’t have done 不可能做过… ;could have done 原来能够做，（却没做成)I could have worked out the problem，but I was too nervou...
