主语从句、表语从句、宾语从句、同位语从句在整个句子中所起的作用,相当于一个名词,因而,这四种从句又通称为名词性从句。名词性从句的时态一致、语序、关联词的使用辨析等是历年高考测试的重点。
1)主语从句
作句子主语的从句叫主语从句。通常由从属连词that,whether,if和连接代词what,who,which,whatever,whoever以及连接副词how,when,where,why等词引导。that在句中无词义,只起连接作用;连接代词和连接副词在句中既保留自己的疑问含义,起连接作用,又在句中充当句子成分。例如:
That the volleyball match will be put off is certain now.
Whether Mr. Smith will go to attend the meeting depends on the weather.
What Mr. Wang has said has nothing to do with the case.
How the situation in the Middle East will develop is anybody's guess.
Who will go to attend the meeting to be held in Beijing hasn't been decided yet.
When and where we shall hold the meeting will be discussed at today's meeting.
Whoever did this should be punished.what可以引导主语从句、宾语从句,意为"the thing(s) that (which)所……的事物(或人)"。
that与what的区别:从句中如果主语和表语或宾语都不缺少时,连接词应用that,否则用what。例如:What we can't get seems better than what we have.主语从句后的谓语动词一般用单数形式,但主语从句中的主语只限定从句中的谓语动词,与主句的谓语动词无关。有时为避免句子头重脚轻,常用形式主语it代替主语从句,而把主语从句置于句末,常用以下句型:
(1)It+be(seem)+adj.+that从句。例如:
It's disappointing that Tom can't come to the celebration.
It is true that Mr. Wang has been seriously ill.
常这样用的形容词有fortunate,funny,good,surprising,true,unusual,wonderful等。
(2)It+be+adj.+that从句(should或动词原形),常用于这种结构中的形容词有anxious,careful,important,necessary,possible等。例如:
It's quite necessary that some immediate efforts(should) be made.
It is advisable that you (should) take care of your health.
(3)It+be+adj.+that...should have done.常用于这种结构的形容词有fit,important,necessary,proper,right,wrong等。例如:It is quite natural that Mr. Henry should have been regarded as one of the best managers of the city.
(4)It+be+(a/an/形容词性物主代词)noun+that...,常用于这种结构的名词有duty,a fact,good news,a good thing,an honour,no wonder,a pity,a reGREt等。例如:
It is a pity that you have missed such a wonderful concert.
(5)It+(not)动词(动词短语)+that...。例如:
It doesn't matter which of the questions is to be discussed first.
It doesn't make much difference whether they come or not.
It happened that the Wangs were out when I called.
It appears that we have come to the wrong conclusion.
(6)在以下结构中,也常用it作形式主语,代替主语从句:
①如全句是被动语态时。例如:
It is said that the novel written by Jia Ping'ao has been translated into many languages.
It is reported that another satellite has been sent into the space by China.
②如该句是疑问句时。例如:
Is it probable that he will raise money for the children who are out of school.
Is it true that Mr.Zhuang has been seriously hurt in the bus accident.
③如该句是感叹句时。例如:
How strange it is that the young boy could work out so many maths problems in a minute!
