動(dòng)詞不定式

　　1、不定式做主語(yǔ)一般表示具體的某次動(dòng)作。

　　To complete the 30-storied building in one year was quite a difficult task.

　　To do that implies taking responsibility.

　　當(dāng)主語(yǔ)較長(zhǎng)，謂語(yǔ)較短時(shí)，常用it做形式主語(yǔ)，而將不定式放到謂語(yǔ)的后面。如：

　　It is important for modern young people to master at least two foreign languages.

　　It做形式主語(yǔ)，不定式放在謂語(yǔ)動(dòng)詞之后常用于下列結(jié)構(gòu)中：

　　A. It is+形容詞+(for/of sb.)+不定式，如：

　　It is not easy to catch fish with your hands only.

　　It is important for us young people to learn English and master it.

　　B. It is+名詞+不定式

　　It is a pity to have to go without her.

　　C. It takes (sb.) some time +不定式

　　It takes me three hours to learn English each day.

　　2、不定式作表語(yǔ)

　　不定式作表語(yǔ)常表示將來(lái)的動(dòng)作，主語(yǔ)常常是表示意向、打算、計(jì)劃的詞(idea, task, purpose)等,如：

　　The most important thing for one’s health is to have plenty of exercise.

　　3、不定式作賓語(yǔ)

　　I like to go out for walks in the warm sunshine in spring.

　　She failed to finish the assignment in time, and she was worried about it.

　　4、“wh-+不定式”結(jié)構(gòu)

　　不定式前加一個(gè)疑問(wèn)代詞(what, which, who, whom, whose)或疑問(wèn)副詞(where, when, how, why)，以及連詞whether構(gòu)成特殊的不定式短語(yǔ)，其作用相當(dāng)于一個(gè)從句，這樣的不定式短語(yǔ)常常在某些動(dòng)詞后面作賓語(yǔ)。

　　I couldn’t decide which book to choose.

　　I can tell you where to get this book.

　　“wh-word+不定式”結(jié)構(gòu)除了作賓語(yǔ)外，還可以在句中作主語(yǔ)或者表語(yǔ)。如：

　　When to start the program remains undecided.

　　The question is how to put the plan into practice.