Unit 4 语法讲解
本单元重要的语法分为以下两部分：
一、 疑问词加不定式的用法。
1. 疑问词加不定式可以在句子中充当不同的成分：
1） 被用于主语。
When to hold the meeting has not yet been decided.
Where to live is a problem.
How to cope with the rising cost of living becomes a daily discussion topic.
2） 被用于宾语。
We must know what to say at a meeting.
He could not tell whom to trust.
Do you know how to play bridge?
Jim is not sure whose to choose.
Mary and John are not certain whether to get married or not.
3） 被用于宾补。
The students ask their teacher when to hand in their work.
4）被用于表语。
The problem is where to find the financial aid.
The question is who to elect.
经典练习：
选择：
1.I have no idea when ___ her the bad news.
A. will tell B. telling
C. tell D. to tell
2. I don’t know ________.
A. how to say B. how to speak
C. what to say it D. what to speak.
翻译：
1. 什么时候开始还没有决定
2. 问题是怎样按时到达那里。
3. 怎样开始比在哪结束更难。
4. 困难的是选择那条路。
二、 must及have to 的用法区别。
must 表示说话人主观认为必要，或法律法规规定，语气较强烈。话人由于客观情况使然，不得不做某事。
经典练习：
Can you play football with us this afternoon?
Sorry, I can’t. I _____ look after my mother at home.
A. must B. have to C. can D. may
to 表示说 Have
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