高中英語語法主語從句與先行解析
高中英語語法主語從句與先行解析
主語從句與先行it
主語從句可以按其引導(dǎo)詞的不同分為三類:
第一類,用從屬連詞that引導(dǎo)的主語從句,例如:
That we shall be late is certain.
That the driver could not control his car was obvious.
這種結(jié)構(gòu)主要是對that從句的內(nèi)容進行強調(diào),屬正式文體,連詞that不可以省略;但是在一般情況下,往往使用先行it結(jié)構(gòu),即用it作形式主語,而把that從句放到后面,這時,在口語中,連詞that有時則可以省略。所以上述兩句可以改為:
It is certain that we shall be late.
It was obvious that the driver could not control his car.
如果整個句子是疑問形式,就只能用先行it結(jié)構(gòu),例如:
Is it true that he would take the risk?
Is it possible that they will come tomorrow?
常使用先行it結(jié)構(gòu),用that從句作主語的句子有下列幾個句型:
1、It + be + 形容詞 + that從句:
It is clear that he was telling the truth.
It’s probable that we’ll be a little late.
2、It + be + 名詞詞組 + that從句:
It’s a pity that you can’t go with us.
3、It + 及物動詞 + 賓語 + that從句:
It worried her a bit that her hair was turning grey.
It shocked me that Peter didn’t tell anybody where he was.
4、It + be + 過去分詞 + that從句:
It is said that he has been there many times.
5、It + seem/happen/appear等不及物動詞 + that從句:
It seems that he has lost something.
注意:
在上述第1和第2兩種句型中,that從句前置與使用先行it,that從句后置在意義上沒有什么差異;但使用先行it結(jié)構(gòu)較為常見。
在第3種句型中,that從句前置在語法上是可能的,但實際上并不常見,通?偸鞘褂孟刃衖t結(jié)構(gòu) .
第4種句型實質(zhì)上是被動結(jié)構(gòu),由于that從句不可以位于句首作被動句的主語,所以只能使用先行it結(jié)構(gòu)。
第5種句型已經(jīng)形成了固定的搭配關(guān)系,that從句不能前置,只能使用先行it結(jié)構(gòu),不過,這種結(jié)構(gòu)可以轉(zhuǎn)換為帶有不定式的簡單句,例如:
It happened that I had no money with me that day.
→ I happened to have no money with me that day.
第二類,用連接代詞who、whose、which、what,連接副詞when、where、how、why,以及連詞whether(或if)引導(dǎo)的主語從句,例如:
Who was responsible for the accident is not yet clear.
→ It is not yet clear who was responsible for the accident.
What he did is not yet known.
→ It is not yet known what he did.
Whether it is true remains a problem.
→ It remains a problem whether / if it is true.
從以上例句可以看出,這類主語從句可以直接放在句首作主語,也可以使用先行it結(jié)構(gòu),把主語從句放在后面,兩種結(jié)構(gòu)可以互換,意義上無差異,但用if 引導(dǎo)主語從句時,只能采取先行it結(jié)構(gòu),也就是說if不可以引導(dǎo)置于句首的`主語從句。
第三類,用what、whatever、where、wherever、whoever、whichever等代詞引導(dǎo)的主語從句,例如:
What he said at the meeting encouraged everyone.
Whoever fails to see this will make a big blunder.
這類從句一般相當于帶有定語從句所修飾的名詞詞組,即在結(jié)構(gòu)上相當于一個名詞加上一個定語從句,例如:
What he wants to buy is a ten-speed bicycle.
→ The thing that he wants to buy is a ten-speed bicycle.
Whoever breaks the law is sure to be punished.
→ Anyone who breaks the law is sure to be punished.
切記,這類主語從句不可以使用先行it結(jié)構(gòu)。
上述第二類主語從句與第三類主語從句盡管在形式上十分相似,但實際上是不同的。第二類結(jié)構(gòu)中用連接代/副詞引導(dǎo)的從句系由特殊疑問句轉(zhuǎn)化而來,以whether/if引導(dǎo)的從句系由一般疑問句轉(zhuǎn)化而來,自然含有疑問的意味,例如:
When they will have the sports meet is still a question.
→ When will they have the sports meet?
Who he is doesn’t concern me.
→ Who is he?
Whether he will join us won’t make too much difference.
→ Will he join us?
而第三類結(jié)構(gòu)中的主語從句則沒有疑問的意味。
試比較下列各句:
① What caused the accident is a complete mystery.
、 What caused the accident was a broken bottle.
、 What she looks like doesn’t matter.
、 What she’d like is a digital watch.
上述各句中盡管都有一個以what引導(dǎo)的主語從句,但其意義不盡相同;第①和③句中的主語從句系由What caused the accident?和What does she look like?轉(zhuǎn)化而來,所以可以改成:
It is a complete mystery what caused the accident.
It doesn’t matter what she looks like.
第②④句中的主語從句含義分別為The thing that caused the accident和The thing which she’d like,所以不含疑問意味,因此不可以說:
It was a broken bottle what caused the accident.
It is a digital watch what she’d like.
但是可以說:
It was a broken bottle that caused the accident.
It is a digital watch that she’d like.
不過,這已不是主語從句,而是強調(diào)結(jié)構(gòu)了。
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