1、四、名词性从句在复合句中，有些从句的作用相当于名词，可以充当主语、表语、宾语或同位语，分别称为主语从句、表语从句、宾语从句、同位语从句。而这些从句又统称为名词性从句。（一）主语从句1 定义：用作主语的从句叫做主语从句。引导主语从句的词有连词that,whether,连接代词 what,who,whom,which;连接副词 when,where,how,why等。2 引导主语从句的关联词有三类：(1) 从属连词 that、whether。如：如：That they were in truth sisters was clear from the facial resemblance betwe
2、en them. 很明显，她们确是亲姐妹，她们的脸型很相似。 Whether hell come here isnt clear. 他是否会来这里还不清楚。 that 引导主语从句只起引导作用，本身无实际意义，在主语从句中不充当任何成分，但不能省略。由 whether 及其他连词引导的主语从句放在句首，句后都可。 If 只能放在句中。比如：很明显他是个好人。他通过了考试让妈妈很高兴。天气是否会转晴还不确定。(2) （特殊疑问词）连接代词 who, whom, whose, what, which, whoever, whatever, whichever 我们需要的是时间。谁将成为我们的班长还
3、没有决定。哪本书更好还不知道。(3) （特殊疑问词）连接副词 where, when, how, why，wherever，whenever，however。 他是怎样成为一名老师的还不清楚。你无论什么时候来都不重要。补充：1 主语从句能用 it 作形式上的主语。常以 it 作形式主语的句型有：A. It+be+形容词(obvious, true, natural, surprising, good, wonderful, funny, possible, likely, certain, probable, etc.)+that 从句。如：很可能他把一切都告诉她了。B. It+be+名词词组
4、(no wonder, an honour, a good thing, a pity, no surprise, etc.)+that 从句。如：很遗憾我们不能去。C. It+be+过去分词(said, reported, thought, expected, decided, announced, arranged, etc.)+that 从句。如：据说格林先生已经到了北京。D. It+seem, happen 等不及物动词及短语+that 从句。如：Alice 似乎不来参加晚会。碰巧我那天外出了。E. It+doesnt matter (makes no difference, etc.
5、)+连接代词或连接副词引起的主语从句。如：她是否来这无关紧要。我们在哪里开会毫无区别。F. 当 that 引导的主语从句出现在疑问句中时，要以 it 作形式主语，而把主语从句后置。下周那位科学家将给我们作报告是真的吗？2注意连接代词 whoever, whatever, whichever 等引导主语从句的含义Whoever comes will be welcome. (whoever=the person who) 来的人将受到欢迎。Whatever he did was right. (whatever=the thing that) 他所做的事情是正确的。Whichever of yo
6、u comes in will receive a prize. (whichever=anyone of you who) 你们当中不论哪个进来将会得到奖励。3. 主语从句需注意的问题(1)主语从句中用陈述语序What she is afraid of is their taking her to Paris. ( What is she afraid of Wrong )(2)主语从句后谓语动词用第三人称单数That they havent phoned is strange.(3)that 引导的主语从句中，that 不可被省略That price will go up is certa
7、in.练习：1. _ as much as one-fifth of all timber harvested is not used.A. The estimate B. The estimate C. They are estimated D. It is estimated that2. _ some mammals came to live in the sea is not known.A. Which B. Since C. Although D. How 3. _ we have achieved is attributed to the guidance of our pare
8、nts.A. Whoever B. Whatever C. However D. That 4. _ wealthy does not necessarily mean that a man is greedy.A. For the reason that he is B. Just because he is C. The reason of being D. That he is 5. Although _ happened in this developed country sounds like science fiction, it could occur elsewhere in
9、the world.A. which B. what C. how D. it6. _ she had forgotten to take her notebook.A. That occurred to her B. She occurred that C. To her that occurred D. It occurred to her that7. I am sure that _ she said is wrong.A. which B. all C. this D. what8. We lost our way in the forest, and _ made matters
10、worse was that it was getting dark.A. that B. which C. it D. what9. _ some mammals came to live in the sea is not known.A. Which B. Since C. Although D. How 10. _ or not is still uncertain.A. Hes coming B. If he is comingC. That coming D. Whether hes coming11. Its _ hell be able to come.A. doubt whe
11、ther B. doubtful C. doubt it D. doubtful whether 12. _ he is at work in the heart of the big city or at home in the quiet suburb, Dicks life is tied to machines. A. Whether B. Till C. If D. Unless13. _ he saw both surprised and frightened him.A. That B. When C. What D. Which14. _ is a spell of warm
12、sunshine.A. What do we all need. B. What all we needC. What we need D. What we all need15. _ is a pity that he should feel so upset. A. What B. That C. He D. It16. _ a spoonful of soil can tell us so much about the structure and early history of the moon.A. Remarkable B. Quite remarkably C. It is re
13、markable that D. It is remarkable fact that17. _ you nominate will be elected. A. Who B. Whom C. Whomever D. Thats 18. _ book you borrow must be returned within a week.A. What B. Which C. Whichever D. Thats 19. _ of us gets home first starts cooking.A. Who B. Which C. Whichever D. Anyone20. _orders
14、he gives are obeyed.A. Whichever B. Which C. Whatever D. What 21. _ at the meeting yesterday is of great importance to the development of our business. A. That we discussed B. What we discussed C. How did we discuss D. What did we discuss 22. _ you say now cant make up for what youve done. A. No matter B. Whatever C. However D. That 23. _ was once regarded as impossible has now become a reality. A. That B. Which C. Who D. What 24. _ you do, do it well. A. What B. Which C. That D. Whatever 25. _ the prisoner escaped is a mystery. A. What B. How C. That D. Which
