高中英语语法——主语从句
2. 由whether引导的主语从句含有"是否"意思的主语从句，连接词不能用if，只能用whether。
例如：
Whether we will hold a party in the open air next week is uncertain. 我们下周是否在户外开晚会还不确定。
3. 由其他连接代词和连接副词引导的主语从句who, which, when, where, why, how等连接代词和连接副词既有疑问含义，又起连接作用，同时在从句中充当各种成分。
例如：
Who she is doesn’t concern me. 她是谁与我无关。
【分析】连接代词who在从句中充当表语。
Where I spend my summer holiday is no business of yours. 我在哪里过暑假不关你的事。
【分析】连接副词where在从句中充当状语。
How the prisoner escaped is a complete mystery. 囚犯如何逃脱完全是一个谜。
【分析】连接副词how在从句中充当状语。
Which car you will choose to buy makes no difference. 你决定买哪一辆车都不会有任何区别。
【分析】"Which car"在从句中充当动词buy的宾语。
4. whatever / whoever的用法
whatever / whoever可以引导主语从句，并在句中作主语、宾语、表语等,不含疑问意义。whatever相当于anything that; whoever 相当于anyone who。
例如：
Whoever wants to enter into this school must take the exam. 任何想进入这所学校的人都必须参加这个考试。
【分析】"Whoever wants to enter into this school"相当于"Anyone who wants to enter into this school"。
Whatever she did was right. 她做的一切都是对的。
【分析】"Whatever she did"相当于"Anything that she did"。
注意！让步状语从句中的whatever相当于no matter what; whoever 相当于no matter who。例如：Whoever wants to enter into this school, he must take the exam. 不论谁想进入这所学校,都必须参加考试。（这是一个让步状语从句,相当于:No matter who wants to enter into this school, he must take the exam.）
二、形式主语it构成的主语从句
1. 由连词that引导的主语从句，在大多数情况下可以用形式主语it代替，即将it放在句首，而将主语从句放在句末，以避免句子头重脚轻。
例如：
It is a matter of common experience that bodies are lighter in water than they are in air. 物体在水中比在空气中轻，这是大家共有的经验。
【分析】形式主语it指代后面的主语从句"that bodies are lighter in water than they are in air"。需要注意的是，it作形式主语时，要注意和as引导的定语从句的区别。试比较:
① It was reported that no country was under the terrorist attack last year.
② As was reported, no country was under the terrorist attack last year.
句意：据报道，去年没有国家遭到恐怖分子的袭击。
【分析】上述两个句子句意相同,但结构不同。前一个句子包括一个主语从句"that no country was under the terrorist attack last year"；后一个句子包括一个非限定性定语从句"As was reported",其中as指代整个主句内容。
2. 由连接代词、连接副词和连词whether引起的主语从句常可用先行词it作主语，而把主语从句放到后面去。
例如：
Who’s to head the delegation hasn’t been made public.
→ It hasn’t been made public who’s to head the delegation. 谁来领导这个代表团还没有宣布。
How many people we are to invite is still a question.
→ It is still a question how many people we are to invite. 我们要邀请多少人还是一个问题。
When we arrive doesn’t matter.
→ It doesn’t matter when we arrive. 我们什么时候到没有关系。
Whether it will do us harm or good remains to be seen.
→ It remains to be seen whether it will do us harm or good. 这对我们有害还是有利还得看一看。
3. 常见用it作形式主语的复合句结构
① It is a fact (a pity / no wonder / a good idea / a shame ...)that ...
例如：It’s a pity that you didn’t come to my birthday party. 你没有来参加我的生日派对真是太遗憾了。
② It is important(necessary / advisable / desirable / imperative / true / strange / possible ...)that ...
需要注意的是，这类主语从句中，谓语动词很多为"(should)＋动词原形"，即要用虚拟语气。例如：
It is necessary that several nurses (should) stay. 几个护士留在这儿是很有必要的。
It is imperative that everyone (should) learn from practice. 每个人都应该从实践中学习。
③ It is reported (well-known / hoped / thought / expected / said / believed / decided / suggested / ordered ...)that ...
例如：It is said that many people was killed in the earthquake. 据说很多人在这次地震中丧生了。
④ It seems(appears / doesn’t matter / makes no difference / ...)that ...
例如：It makes no difference whether he will attend the meeting or not. 他是否会参加会议都无关紧要。
三、主语从句中的否定前移
当用it作形式主语，而将主语从句放在句尾时，主语从句中的否定词常要前移至主句中。例如：
It doesn’t seem that they are from the same university. 看来他们不是来自同一所大学。
It doesn’t appear that we’ll have a sunny day tomorrow. 看来我们明天不会碰上好天气。
【真题演练】
请找出下列句子中的错误选项并改正。
1. There are backward towns on the edge of Bombay or Brasilia,
A B
just as there were on the edge of seventeenth-century London or
C
early nineteenth-century Paris. This is new is the scale.
D
2. What fashion differs from country to country may reflect the
A B C
cultural differences from one aspect.
D
3. What caused the accident and who was responsible for it
A B C
remains a mystery to us.
D
答案及解析
1. D。句意：现在孟买或巴西利亚周边有一些落后的城镇，正如17世纪伦敦和19世纪初巴黎周边也有一些落后的城镇一样。不同的是规模。
分析：句子“This is new is the scale.”显然不合语法，句意也说不通。根据上下文判断出其句意为“不同的是规模”，所以本句需要的是一个由what引导的主语从句，同时what在主语从句中充当主语成分。故本题选D，This →What。
2. A。句意：国与国之间的时尚差异可以从一个方面反映出文化的差异。
分析：分析句子结构可以看出“What fashion differs from country to country”在本句中作主语从句，再分析该从句可以看出关系代词what用得不准确，因为如果用what引导主语从句，what要在从句中充当主语、宾语或表语成分，而本句的主语从句是一个完整的句子，不需要补充任何成分，而只需要一个连接词，所以“What”应改为“That”，故本题选A。
3. D。句意：是什么引起了这次事故以及事故由谁来负责对我们来说仍然是个谜。
分析：两个由and 连接的并列主语从句作主语，如果表示两件事，动词用复数。“引起事故的原因”和“由谁负责”，显然是两件事，所以要把remains改为remain，故本题选D。