一、主語(yǔ)從句是在復(fù)合句中充當(dāng)主語(yǔ)的從句，通常放在主句謂語(yǔ)動(dòng)詞之前或由形式主語(yǔ)it代替，而本身放在句子末尾。
1. It 作形式主語(yǔ)和it引導(dǎo)強(qiáng)調(diào)句的比較：
It 作形式主語(yǔ)代替主語(yǔ)從句，主要是為了平衡句子結(jié)構(gòu)，主語(yǔ)從句的連接詞沒(méi)有變化。而it引導(dǎo)的強(qiáng)調(diào)句則是對(duì)句子某一部分進(jìn)行強(qiáng)調(diào)，無(wú)論強(qiáng)調(diào)的是什么成分，都可用連詞that。被強(qiáng)調(diào)部分指人是也可用who/whom。例如：
It is a pity that you didn’t go to see the film.
你沒(méi)有去看這個(gè)電影，多可惜??！
It doesn’t interest me whether you succeed or not.
對(duì)于你是否成功，我并不感興趣。
It is in the morning that the murder took place.
兇殺案發(fā)生的時(shí)間是在早上。
It is John that broke the window.
打碎窗戶的是約翰。
2.用it 作形式主語(yǔ)的結(jié)構(gòu)
(1)It is ＋名詞＋從句
It is a fact that … 事實(shí)是… It is an honor that …非常榮幸 It is common knowledge that …是常識(shí)
It’s a pity that you missed the exciting football match.
多么可惜啊，你錯(cuò)過(guò)了一場(chǎng)精彩的足球比賽。
(2)it is ＋形容詞＋從句
It is natural that… 很自然… It is strange that… 奇怪的是…
It is uncertain whether he can come to Jenny’s birthday party or not.
他來(lái)不來(lái)參加簡(jiǎn)的生日派對(duì)，這個(gè)不確定。
(3)it is ＋不及物動(dòng)詞＋從句
It seems that… 似乎… It happened that… 碰巧…
It seemed that he didn’t tell the truth.
似乎他沒(méi)有講真話。
It happened that I was out when he called.
碰巧，他打電話的時(shí)候我在外面。
(4)it ＋過(guò)去分詞＋從句
It is reported that… 據(jù)報(bào)道… It has been proved that… 已證實(shí)…
It is reported that 16 people were killed in the earthquake.
據(jù)報(bào)道，在這場(chǎng)地震中，有16人遇難。
?