Section_ⅢGrammar—主语从句语法图解探究发觉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.③What is even more important is that as the earth cooled down, water began to appear on its surface.④It was not immediately obvious that water was to be fundamental to the development oflife.⑤What many scientists believe is that the continued presence of water allowed the earth to dissolve harmful gases 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.[我的发觉](1)以上黑体部分在句中作主语。

(2)①句中的what在从句中作表语，但⑤句中的what在从句中作宾语；③句中的what在从句中作主语。

(3)②⑥句中的whether意为：是否。

(4)④句中it是形式主语，真正的主语是后面that引导的从句。

一、定义在主从复合句中充当主语的从句即为主语从句。

What made people excited was that the solar ship had completed around-the-world trip.让人们感动的是太阳能船已完成了环游世界的旅行。

It worried the woman that her son was always playing computer games.儿子始终在玩电脑玩耍，这让这个女人很担忧。

二、主语从句的连接词及其句法功能1．连接词that和whether/if(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，但不行省略。

That she survived the accident is a miracle.她在事故中幸免于难简直是奇迹。

(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”，不行省略。

Whether the plan will be carried out is still unknown.＝It is still unknown if/whether the plan will be carried out.这个方案是否会实施还不知道。

[名师点津]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]补全句子①That_she_could_come_to_help_us made us very happy.她能来挂念我们使我们很兴奋。

②Whether_she_is_coming_or_not doesn't matter too much.她来不来都无关紧要。

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。

Whichever (of you) comes in first will receive a prize.无论(你们)谁先到都可以得奖。

Who will go to the concert is not known.不知道谁会去听音乐会。

Whatever you do in your spare time should do no harm to others.无论你在业余时间做什么都不应当损害其他人。

[名师点津]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。

How this happened is not clear to anyone.这件事怎样发生的，谁也不清楚。

When we will have a meeting is an important question.我们何时进行会议是个重要的问题。

Where I spend my summer is no business of yours.我在哪里过暑假不关你的事。

[名师点津]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；(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]用适当的连接代词或连接副词填空①How it was done was a mystery.②Why John was late for the class has been unexplained.③Which part of the country he will travel to needs discussing.④Where/When the English evening will be held has not yet been decided.⑤What surprises me most is that he is too proud.⑥Whoever is interested in the activity can sign your names.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 important that he should know about this.他应当知道此事是重要的。

[名师点津]在“It＋be＋形容词＋主语从句”结构中，若形容词为important/necessary/strange等，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 he didn't come.很圆满他没来。

3．It ＋be＋过去分词(said, reported, thought, expected, proved, etc.)＋主语从句It is suggested that the meeting be put off.有人建议会议延期召开。

[名师点津]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，主语从句中的谓语用“(should) do”。

4．It＋不及物动词(happen, seem, appear, remain, etc.)＋主语从句It seems that it is going to rain.看起来好像要下雨。

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](1)补全句子①It's_a_pity that you can't attend my birthday party.很惋惜你不能参与我的生日聚会。

②It's_suggested that the old man should go to the countryside to have a rest.建议这位老人到乡村休息一下。

③It_seems_to_me that you disagree with the plan.在我看来，你好像不赞成这个方案。

④It is doubtful whether_she_will_be_able_to_come_to_the_party.她是否能来参与聚会还很难说。

⑤It_happened_that the harvest was bad that year.碰巧那年收成不好。

(2)句型转换(每空一词)①That he suddenly fell ill last month surprised us.→Itsurprisedusthat he suddenly fell ill last month.②Whether they will sell the house hasn't been yet decided.→Ithasn'tbeendecidedyetwhether they will sell the house.③That light travels in straight lines is known to us all.→Itisknowntousallthat light travels in straight lines.四、主语从句中应留意的问题1．从句要用陈述语序What we will do next should be decided.应当打算一下我们下一步该做什么。

2．主谓全都(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。

[名师点津]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全都。

What the school needs most are books.这所学校最需要的是书。

(2)假如由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。