掌握英語語法是學習英語最基本的一項技能，全國英語等級考試三級考試大綱要求考生掌握一些基本的英語語法，能在閱讀、寫作等過程中正確運用這些知識，達到正確理解、獲取信息及表達思想的目的。希賽網(wǎng)英語三級頻道為大家分享全國英語等級考試三級語法常考知識點。

名詞性從句用法及示例：

1.引導名詞性從句的連接詞

引導名詞性從句的連接詞可分為三類：

連接詞：that,whether,if(不充當從句的任何成分)

連接代詞：what,whatever,who,whoever,whom,whose,which

連接副詞：when,where,how,why

不可省略的連詞：

1.介詞后的連詞

2.引導主語從句和同位語從句的連詞不可省略。例如：

That she was chosen made us very happy.她被選上了，我們很高興。

We heard the news that our team had won.我們聽到消息說我們隊贏了。

比較：whether與if均為"是否"的意思。但在下列情況下，whether不能被if取代：

1.whether引導主語從句并在句首

2.引導表語從句

3.whether從句作介詞賓語

4.從句后有"or not"

大部分連接詞引導的主語從句都可以置于句末，用it充當形式主語。例如：

It is not important who will go.誰去，這不重要。

It is still unknown which team will win the match.到底誰贏呢，形勢尚不明朗。

2名詞性that-從句

1)由從屬連詞that引導的從句叫做名詞性that-從句。That只起連接主句和從句的作用，在從句中不擔任任何成分，本身也沒有詞義。名詞性that-從句在句中能充當主語、賓語、表語、同位語和形容詞賓語。例如：

主語：That he is still alive is sheer luck.他還活著全靠運氣。

賓語：John said that he was leaving for London on Wednesday.約翰說他星期三要到倫敦去。

表語：The fact is that he has not been seen recently.事實是近來誰也沒有見過他。

同位語：The fact that he has not been seen recently disturbs everyone in his office.

近來誰也沒有見過他，這一情況令辦公室所有的人不安。

形容詞賓語：I am glad that you are satisfied with your job.你對工作滿意我感到很高興。

2)That-從句作主語通常用it作先行詞，而將that-從句置于句末。例如：

It is quite clear that the whole project is doomed to failure.很清楚，整個計劃注定要失敗。

It's a pity that you should have to leave.你非走不可真是件憾事。

用it作形式主語的that-從句有以下四種不同的搭配關(guān)系：

a.It+be+形容詞+that-從句

It is necessary that…有必要……

It is important that…重要的是……

It is obvious that…很明顯……

b.It+be+-ed分詞+that-從句

It is believed that…人們相信……

It is known to all that…從所周知……

It has been decided that…已決定……

c.It+be+名詞+that-從句

R>It is common knowledge that………是常識

It is a surprise that…令人驚奇的是……

It is a fact that…事實是……

d.It+不及物動詞+that-分句

It appears that…似乎……

It happens that…碰巧……

It occurred to me that…我突然想起……