北京学位英语测试重点：不定式应注意的问题
1、关于不定式的作用
1）不定式作主语时，若主语较长而谓语较短，常以作句首形式而不定式放在句末
It’s illegal to drive without a license.
It is human to want something better.
2）在think, consider, believe, find, know, declare, guess, prove, suppose, imagine等词后面常接“to+be+形容词/名词/反身代词结构”作宾补，但to be常可省略
All her friends supposed her (to be)dead.
We sometimes imagine a desert island (to be) a sort of paradise, where sun always shines.
3）在序数词，形容词/副词的最高级，和the last, the only后，常用不定式作定语
She was the only one to survive the crash.
He loves parties; he is always the first to come and last to leave.
4）“介词+which+不定式’可作定语，which代替前面的中心词
You have a number of topics from which to choose.
She had no time left in which to pack her things.
5）“连接词what/which/when/where/who/why/how等+不定式”可作主语，宾语，宾补，表语等。
What to do next remains undecided.
Our difficulty is how to get enough food.
He discovered how to open the safe.
2、关于不定式的时态
1）一般式to do表示的动作在谓语动词表示的动作之后发表；
进行式to be doing可表示该动作正在发生，或与谓语动作同时进行；
完成式to have done表示的动作在谓语动作表示的动作之前发生。
They all agreed to give up this plan.
I happened to be standing next to him when he collapsed.
He pretended not to have seen me.
2）expect, hope, intend, mean, plan, suppose, think, want, wish等词的过去式完成时态+不定式的一般形式；would/should like +不定式的完成时态表示过去未曾实现的愿望，打算或意图。
I had intended to call on to you ,but was prevented from doing so.
He would like to have attended the meeting, but he was ill.
3、关于不定式的语态
1）当不定式与其修饰的词之间有动宾关系，并且与句中主/宾/表语有逻辑上的主谓关系时，用主动形式表示被动含义。
We have many difficulties to overcome.
I’ll show you the right path to take.
2）当不定式作表语/宾补形容词的状语，又与句中的主语或宾语有逻辑上动宾关系时，用主动形式表示被动含义
Some books are interesting to read, but boring to learn.
They found the subject hard to understand
3）在there be句型中修饰的主语的不定式常用主动形式
There is nothing to see.
There are a lot of letters to answer this night.
4、关于不定式的逻辑主语
1）不定式的逻辑主语/复合不定式常用“for+名词/代词宾格+不定式”结构
It is difficult for me to drive in the mountains.
It is a great honor for us to be present at the party.
2）在表示人物性格特征或感情色彩的形容词后，常用of引出不定式的逻辑主语，如：absurd（荒唐的），brave, careful, careless, clever, considerate, courageous, cruel, foolish, generous, good（友善）,graceful, honest, kind, nice, polite, right, rude, silly, stupid, thoughtful, wicked（邪恶的），wise, wrong, generous, unwise.
It was unwise of him to make that silly remark.
It was very thoughtful of her to come to see me when I was ill.
5、不定式省略to的情况
1）主动语态中，以下表达后接省略to的不定式：look at, notice, see, watch, observe, hear, listen to feel, have, make, let, cannot but, do nothing/anything but, had better, had best, would rather(……than), would sooner, would just as soon, might as well
I would sooner resign than work under that boss.
You’d better remain where you are.
2）在why和why not后常接省to的不定式构成问句
Why worry about such trifles?
Why not wait for a couple of days?
3）在介词but和except前若有实义动词do的各种形式，后接省略to的不定式
We had nothing to do but cancel the meeting
I don’t have any choice but/except to give up the plan.
4）在下列固定搭配中常用省略to的不定式：leave/let go（放开）,let slip（失言，错过）,make do（凑合）,make believe（假装），haer say /tell（听说）
He made believe he was innocent.
Don’t let slip such a good opportunity to learn
Make that dog leave go my coat.
5）两个不定式结构由and, or , but, except, than相连时，第二个不定式省略to
He hardly knew whether to laugh or cry.
It is easier to persuade people than force them
