文档介绍：Unit 1 Module 5
Grammar and usage
To-infinitive and
Verb-ing form as a noun
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Part 1
To-infinitive
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1. to do as a subject
The cat said, “to take roller coaster is terrible ”.
The cat said, “It’s terrible to take roller coaster.”
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How long did it take you to take roller coaster?
How terrible it is to take roller coaster!
不定式短语作主语时, 可以直接放在句首, 但在很多情况下, 尤其是在疑问句和感叹句中, 往往放在谓语之后, 而用先行代词it作形式主语。
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It作形式主语,不定式作真主语常见句型:
It’s my duty to teach you how to learn English well.
It requires patience to be a good teacher.
a) It is + adj. (easy, important,
difficult…) + 不定式
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b) It is + n. (a pity, a pleasure, one’s duty, a shame…) + 不定式
c) It takes/needs/requires + some time (hours, months, days, patience…) + 不定式
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2. to do as a predictive
Our most important task now is to make a plan.
当句子的主语是aim, idea, policy, question, suggestion, wish, task, duty, job, purpose等或者主语是what引导的名词性从句时，后面可以用不定式做表语，用以说明主语所包含内容。
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注: 作表语的不定式都带to, 但当主语部分有实义动词do时, to可以省略。
Now the only thing we can do is wait.
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当不定式充当表语的时候, 表示具体动作或是将来要发生的动作。如:
1. My wish is to be a doctor.
2. What she wants to do is to tell you a secret.
3. His plan is to go abroad and continue his studies.
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PS: 动名词和不定式同样都可以充当表语,两者的区别在于不定式表达是具体或是将来发生动作，而动名词则表示抽象的一般行为。
1. His job is delivering the letters to their destinations.
2. My job is to look after the sister when Mom is cooking.
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