wh-词 + to-v

我们知道,带 wh-疑问词的动词不定式最常用作动词的宾语:

I don't know what to say/who(m) to speak to/which one to buy/when to start out/how to start the motor/where to put my hat/why to go at all/whether to buy it

由此可以证明，上句中的动词不定式短语 which sweater to buy 是做 decide 的宾语，而在动词

不定式短语中 which sweater 又是动词不定式 to buy 的宾语, 再看下面的实例:

1. I couldn't decide which bicycle to buy. 我不能决定买哪辆自行车。

2. We must decide which one to buy. 我们必须决定买哪一个。

3. Ask him when to open it. 问他什么时候(把它)打开。

4. I can't decide where to go for our holidays. 我不能决定假期去哪里。

5. We can't decide whom to invite. 我们不能决定邀请谁。

6. I told her how to find me. 我告诉她怎么找到我。

7. I don't know whether to answer it. 我不知道是否需要回答。

8. As soon as the reporters know what to write about, they get down to work. 采访记者们一知道他们所要写的新闻，就着手工作。

应当注意,这种动词不定式短语含有情态含义:should。它相当于一个带 should 的宾语从句:

1. I can't decide which sweater to buy! = I can't decide which sweater I should buy!

2. I don't know what to say. = I don't know what I should say.

这里应当附带指出，含 wh-疑问词的动词不定式还可以充当主语(A)、表语(B)、介词宾语(C)和定语(D)等。

A. 1. How to isolate radioactive elements was discovered by the Curies. 如何分离放射性元素是居里夫妇发明的。

2. What to do next hasn't been discussed. 下一步做什么还没有讨论呢。

B. 1. What I want to know is where to begin. 我想要知道的是在哪里开始。

2. The question is how to put it into practice. 问题是如何把它付诸实施。

C. 1. Bill said something to Cohn about what to do. 彼尔对科恩说了几句话,告诉他应该做什么。

2. They exchanged views on the question of whom to elect. 关于应当选谁的问题,他们交换了意见。

3. This book is on how to use a computer. 这本书所论述的是如何使用计算机。

D. 1. The key with which to open the door has been lost. 开这扇门的钥匙不见了。

2. We moved to the country so that the children have a garden in which to play. 我们搬到了乡下,这样孩子们就有一个花园游玩了。

wh-疑问词 + 动词不定式结构是常考题型, 不可等闲视之。