不定式作后置定语常表示动作将要发生，它的时态和语态形式在一般情况下是不难理解和使用的。如:
This is the best way to lose weight. 这是最好的减肥方法She is looking for a place to live.她正在寻找一个住处。但不定式作后置定语还有几种特殊情况:
1.当不定式与所修饰的名词(直接宾语)为动宾关系，而间接宾语是不定式的逻辑主语时，此不定式宜用主动形式。如:
Would you bring me a chair to sit on? 请你给我拿张椅子坐好吗?
Please lend me a pen to write with. 请借支钢笔给我用用。
2.当不定式的动作与不定式所修饰的名词有动宾关系，且句中又无它的逻辑主语时，不定式常用被动形式(该不定式短语相当于一个含被动语态的定语从句)。如:
Are you going to the meeting to be held (which is to be held)this afternoon? 你打算去参加今天下午举行的会议吗?
The medical team to be sent (which is to be sent) to the flooded-stricken areas will start of next month.派往洪灾地区的医疗队下个月即将起程。
3.当不定式所修饰的名词是have，get，need 等动词的宾语，且不定式与所修饰的名词也有动宾关系时，不定式既可用主动语态也可用被动语态，但其含义有所不同。如:
Do you have a letter to post?你有信要寄吗?(to post 的动作执行者是"you")
Do you have a letter to be posted?你有信要(我或别人)寄吗?(to be posted的动作执行者不是"you"，而是I或someone else)。又如:
Have you got anything to do this afternoon?今天下午你有什么事要做吗?(自己做)
Have you got anything to be done this afternoon?今天下午你有什么事要人做吗?(别人做)
有少数动词的不定式用于某些动词的宾语后作定语时，如果不定式的逻辑主语就是句子的主语，则要用主动形式表示被动意义。这类动词以have为代表，主要包括have, have got, get, want, need等。如：
I have some letters to write. 我有一些信要写。
I want something to drink. 我想喝点什么。
I want to get something to read. 我想找点东西阅读。
如果不定式的逻辑主语不是句子的主语，则应用被动式，比较：
I have something to type. 我有些东西要打(字)。(指自己打字)
I have something to be typed. 我有些东西要打(字)。(指请人打字)
4.在there be句型中，修饰主语的不定式如果与主语有逻辑上的动宾关系则既可以用主动形式，也可用被动形式。如:
There are three experiments to do/to be done.有三个实验要做,There is nothing to fear /to be feared. 没什么可怕的。
但在 there be 句型中,修饰主语的不定式用主动形式与用被动形式略有区别。
如:
There is nothing to do now,(=We have nothing to do now.)没有事情可干。There is nothing to be done now,(=We can do nothing now.)对于此事毫无力
练一练:
1.With many a problem, I felt worried all the time.
A. to settle B, to be settled C. settling D. being settled
2.Among the experiments is a search for Martian's life.
A. to be carrying out B. to have carried out
C. to carry out D. to be carried out
3. Failure frees one to take risk because there's less
A. to be losing B. to lose
C. losing D. being lost
4. I haven't decided which hotel
A. stay B. is to stay at
C. to stay at D. is for staying
5. He is not a man before difficulties.
A. to be bowed B. to bow
C. bowing D. being bowed
答案：ADBCB