17. 名詞性從句
在句子中起名詞作用的句子叫名詞從句 (Noun Clauses)。 名詞從句的功能相當于名詞詞組, 它在復合句中能擔任主語、賓語、表語、同位語、介詞賓語等，因此根據它在句中不同的語法功能，名詞從句又可分別稱為主語從句、賓語從句、表語從句和同位語從句。
17.1 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。
That she was chosen made us very happy.
We heard the news that our team had won.
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"
Whether he will come is not clear.
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。
It is not important who will go.
It is still unknown which team will win the match.
17.2 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，這一事實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
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……
17.3 名詞性wh-從句
1)由wh-詞引導的名詞從句叫做名詞性wh-從句。Wh-詞包括who, whom,. whose, whoever, what, whatever, which, whichever等連接代詞和where, when, how, why等連接副詞。Wh-從句的語法功能除了和that-從句一樣外，還可充當介詞賓語、賓語補語和間接賓語等，例如：
主語： How the book will sell depends on its author.書銷售如何取決于作者本人。
直接賓語：In one’s own home one can do what one likes.在自己家里可以隨心所欲。
間接賓語：The club will give whoever wins a prize.
俱樂部將給得勝者設獎。
表語： My question is who will take over president of the Foundation.我的問題是誰將接任該基金會主席職位。
賓語補足語：She will name him whatever she wants to. 她高興給他起什么名字就取什么名字。
同位語：I have no idea when he will return.
我不知道他什么時候回來。
形容詞賓語：I’m not sure why she refused their invitation. 我尚不能肯定她為什么拒絕他們的邀請。
介詞賓語：That depends on where we shall go.
那取決于我們去哪兒。
2)Wh-從句作主語也常用先行詞it做形式主語，而將wh-從句置于句末，例如：
It is not yet decided who will do that job.
還沒決定誰做這項工作。
It remains unknown when they are going to get married. 他們何時結婚依然不明。
17.4 if, whether引導的名詞從句
1)yes-no型疑問從句
從屬連詞if, whether引導的名詞從句是由一般疑問句或選擇疑問轉化而來的，因此也分別被稱為yes-no型疑問句從句和選擇型疑問從句，其功能和wh-從句的功能相同， 例如：
主語：Whether the plan is feasible remains to be proved. 這一計劃是否可行還有等證實。
賓語：Let us know whether / if you can finish the article before Friday.請讓我們知道你是否能在星期五以前把文章寫完。
表語：The point is whether we should lend him the money.問題在于我們是否應該借錢給他。
同位語：They are investigating the question whether the man is trustworthy.他們調查他是否值得信賴。
形容詞賓語： She’s doubtful whether we shall be able to come. 她懷疑我們是否能夠前來。
介詞賓語： I worry about whether he can pass through the crisis of his illness.我擔心他是否能度過疾病的危險期。
2)選擇性疑問從句
選擇性疑問從句由關聯詞if/whether…or或whethe…or not構成，例如：
Please tell me whether / i f they are Swedish or Danish. 請告訴我他們是瑞典人還是丹麥人。
I don’t care whether you like the plan or not.我不在乎你是否喜歡該計劃。
17.5 否定轉移
1) 將think, believe, suppose, expect, fancy, imagine等動詞后面賓語從句的否定詞轉移到主句中，即主句的謂語動詞用否定式，而從句的謂語動詞用肯定式。
I don’t think I know you.我想我并不認識你。
I don’ t believe he will come.我相信他不回來。
注意：若謂語動詞為hope,賓語從句中的否定詞不能轉移。
I hope you weren’t ill. 我想你沒有生病吧。
2) 將seem, appear 等后的從句的否定轉移到前面。
It doesn’t seem that they know where to go.
看來他們不知道往哪去。
It doesn’t appear that we’ll have a sunny day tomorrow.
看來我們明天不會碰上好天氣。
3) 有時將動名詞，介詞短語或整個從句的否定轉變為對謂語動詞的否定。
I don’t remember having ever seen such a man.
我記得從未見過這樣一個人。 (not否定動名詞短語 having…)
It’s not a place where anyone would expect to see strange characters on the street.
在這里，人們不會想到在街上會碰上陌生的人。
(anyone 作主語，從句中的謂語動詞不能用否定形式。)
4) 有時狀語或狀語從句中否定可以轉移到謂語動詞前。
The ant is not gathering this for itself alone.(否定狀語)螞蟻不只是為自己采食。
He was not ready to believe something just because Aristotle said so. (否定because狀語) 他并不因亞里斯多德說過如何如何，就輕信此事。
She had not been married many weeks when that man’s younger brother saw her and was struck by her beauty.(否定狀語many weeks)她結婚還不到幾個月，這個人的弟弟就看見她了，并對她的美貌著了迷。
