[语法初识]
原句感知 ①What it was to become was uncertain until between 4.5 and 3.8 billion years ago when the dust settled into a solid globe. ②The earth became so violent that it was not clear whether the shape would last or not. (1)以上各句皆为主从复合句，句中黑体部分为名词性从句作主语，称之为主语从句。 自主探究 ③What is even more important is that as the earth cooled (2)what引导主语从句，what在down, water began to appear on its surface. 从句中作表语(句①)，主语(句④It was not immediately obvious that water was to be ③)，及宾语(句⑤)。 fundamental to the development of life. (3)whether引导主语从句，意为：⑤What many scientists believe is that the continued 是否(句②⑥)。 presence of water allowed the earth to dissolve harmful gases (4)可用it作形式主语，真正的主and acids into the oceans and seas. ⑥So whether life will continue on the earth for millions of years to come will depend on whether this problem can be solved. [语法剖析]
语法点一 在主从复合句中充当主语的从句即为主语从句。 What made her happy was that she won the game in such an important match. 令她高兴的是在这么重要的比赛中她获胜了。
It is decided that the meeting has been put off till next Monday. 已经定下来将会议推迟到下周一了。
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语为名词性从句(句④由that引导主语从句)。 定义 语法点二 1.连接词that和whether/if 主语从句的连接词及其句法功能 (1)that在从句中不充当任何句子成分，本身无任何意义，只起连接作用，但不可省略。 That we are invited to the concert this evening is good news to us. 我们被邀请去参加今晚的音乐会，这对我们来说是个好消息。
(2)whether/if在从句中不充当任何句子成分，起连接作用，意为“是否”，不可省略。 Whether the plan will be carried out is still unknown. ＝ It is still unknown if/whether the plan will be carried out. 这个计划是否会实施还不知道。
[点津] whether引导的主语从句既可放在句首也可放在句尾，但if引导的主语从句只能放在句尾，前面需用it作形式主语。
即时演练1 完成句子
①That_she_could_come_to_help_us made us very happy. 她能来帮助我们使我们很高兴。
②Whether_he_can_finish_his_task_on_time is of great importance. 他能否按时完成任务非常重要。
2．连接代词(who, whose, whom, what, which, whichever, whoever, whomever, whatever等)。连接代词引导主语从句，在从句中可以作主语、宾语、表语或定语。
Who will go to the concert is unknown. 不知道谁会去听音乐会。
Whoever did this job must be rewarded. 无论谁做了这项工作一定要得到酬谢。 What the lecturer said is of great value. 演讲者所讲的非常有价值。
[点津] who 引导的主语从句表示一件“事情”，而whoever引导的主语从句指“人”。 3．连接副词(when, where, how, why等)。连接副词引导主语从句并在从句中作状语。 When we will have a meeting is an important question. 我们何时举行会议是个重要的问题。
How they will solve the serious problem hasn't been decided. 他们将怎样解决这个严重的问题还没有决定。 [点津] 名词性从句引导词的确定步骤：
(1)分析句式结构，明确名词性从句在句中的功能； (2)明确名词性从句所表达的意义；
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(3)明确名词性从句中所需要的成分及意义； (4)确定从句的引导词。
即时演练2
用连接代词或连接副词填空并写出它们在从句中所作的语法成分 ①Why John was late for the class has been unexplained.状语 ②Which part of the country he will travel to needs discussing.定语 ③Where cars will be parked in the future is a question.状语 ④What we should do next remains unknown.宾语
⑤Whoever is interested in the activity can sign your names.主语
语法点三 主语从句中用it作形式主语的结构 1.It＋be＋形容词(obvious, true, natural, strange, etc.)＋主语从句 It is doubtful whether she will be able to come to the party. 她是否能来参加聚会还很难说。
It is necessary that a college student (should) master one or two foreign languages. 大学生掌握一两门外语是必要的。
[点津] 在“It＋ be＋形容词＋主语从句”结构中，若形容词为important/necessary/ strange等时，主语从句中的谓语用“(should) do”。
2．It ＋ be＋名词词组(no wonder, an honour, a pity, a/no surprise, etc.)＋主语从句 It's a pity that you missed the film. 你没有看那部电影真是太遗憾了。
3．It ＋be＋过去分词(said, reported, thought, expected, proved, etc.)＋主语从句 It is reported that no passengers were injured in the accident. 据报道在这起事故中没有乘客受伤。
[点津] 在“It ＋ be＋过去分词＋主语从句”结构中，过去分词若为suggested/ordered/ required/advised等时，主语从句中的谓语用“(should) do”。 4．It＋不及物动词(happen, seem, appear, etc.)＋主语从句 It happened that I was out that day. 碰巧那天我不在。
5．It ＋ 及物动词＋宾语＋主语从句
It surprised him why they came to visit him suddenly. 让他吃惊的是他们为什么突然都来看他。 即时演练3 句型转换
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①That he suddenly fell ill last month surprised us. →It surprised us that he suddenly fell ill last month. ②Whether she will come or not doesn't matter. →It doesn't matter whether she will come or not. ③That light travels in straight lines is known to us all. →It is known to us all that light travels in straight lines.
语法点四 1.从句要用陈述语序 How he succeeded is still a puzzle. 他是如何成功的仍然是个谜。 2．主谓一致
(1)从句作主语时，主句的谓语一般用单数形式。
Where he will get a job after graduation has puzzled him much. 毕业后到哪儿找份工作使他很困惑。
[点津] what引导主语从句时，有时主句谓语动词应与主句中作表语的名词保持一致。 What the school needs most are books. 这所学校最需要的是书。
(2)如果由and连接两个或两个以上的主语从句作主语时，谓语动词用复数；由两个或多个连接词引导一个主语从句时，谓语动词用单数。
When they will start and where they will go have not been decided yet. 他们将在什么时候动身以及要去哪里还没定下来。 When and where they will hold the meeting is not clear. 他们何时何地召开会议还不清楚。
即时演练4 单句改错
①When will we set off is still under discussion. will_we→we_will ②What he needs most are money.are→is
③When and where the meeting will be held have not been decided.have→has ④That the coal workers are still alive are a wonder. 第二个are→is
主语从句中应注意的问题 4
[链接高考]
单句语法填空
1．(2016·江苏高考)It is often the case that anything is possible for those who hang on to hope.
2．(2016·北京高考)Your support is important to our work. Whatever you can do helps. 3．(2015·江苏高考)Where Li Bai, a great Chinese poet, was born is known to the public, but some won't accept it.
4．(2015·北京高考)How we understand things has a lot to do with what we feel. 5．(2014·大纲版全国卷)Exactly when the potato was introduced into Europe is uncertain, but it was probably around 1565.
6．(2014·陕西高考)When the delayed flight will take off depends much on the weather. 7．(2014·天津高考)I think what impresses me about his painting is the colours he uses. 8．(2014·北京高考)Some people believe what has happened before or is happening now will repeat itself in the future.
9．(2013·北京高考)What makes the book so extraordinary is the creative imagination of the writer.
10．(2013·四川高考)What you said at the meeting describes a bright future for the company.
[针对演练]
Ⅰ.句型转换
1．He couldn't understand that, as a teacher of Chinese, he had been asked to teach history. →What he couldn't understand was that, as a teacher of Chinese, he had been asked to teach history.
2．When and where to go on a business trip hasn't been decided. →It hasn't been decided when and where to go on a business trip. 3．We don't know who will take the place of Mr Smith. →Who will take the place of Mr Smith isn't known to us. 4．My uncle happened to be out when I visited him on Sunday. →It happened that my uncle was out when I visited him on Sunday. 5．Whether the old couple will like the trip abroad or not remains to be seen. → It remains to be seen whether the old couple will like the trip abroad or not.
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