例如：
　　It is a pity that you didn’t go to see the film.
　　It doesn’t interest me whether you succeed or not.
　　It is in the morning that the murder took place.
　　It is John that broke the window.

　　2. 用it 作形式主语的结构。
　　(1) It is +名词+从句
　　It is a fact that … 事实是…
　　It is an honor that …非常荣幸
　　It is common knowledge that …是常识

　　(2) it is +形容词+从句
　　It is natural that… 很自然…
　　It is strange that… 奇怪的是…
　　(3) it is +不及物动词+从句
　　It seems that… 似乎…
　　It happened that… 碰巧…

　　(4) it +过去分词+从句
　　It is reported that… 据报道…
　　It has been proved that… 已证实…

　　3. 主语从句不可位于句首的五种情况。
　　(1) if 引导的主语从句不可居于复合句句首。
　　(2) It is said ， (reported) …结构中的主语从句不可提前。
　　例如：
　　It is said that President Jingo will visit our school next week. (right)
　　That President Jiang will visit our school next week is said. (wrong)

　　(3) It happens…， It occurs… 结构中的主语从句不可提前。
　　例如：
　　It occurred to him that he failed in the examination. (right)
　　That he failed in the examination occurred to him. (wrong)

　　(4) It doesn’t matter how/whether …结构中的主语从句不可提前。
　　例如：
　　It doesn’t matter whether he is wrong or not. (right)
　　Whether he is wrong or not doesn’t matter. (wrong)

　　(5) 含主语从句的复合句是疑问句时，主语从句不可提前。
　　例如：
　　Is it likely that it will rain in the evening? (right)
　　Is that will rain in the evening likely? (wrong)

　　4. What 与that 在引导主语从句时的区别。
　　What 引导主语从句时在句时在从句中充当句子成分，如主语.宾语.表语，而that 则不然。
　　例如：
　　1) What you said yesterday is right.
　　2) That she is still alive is a consolation.

　　二.宾语从句
　　宾语从句就是在复合句中作宾语的名词性从句，通常放在主句谓语动词(及物动词)或介词之后。
　　1. 作动词的宾语。
　　(1) 由that引导的宾语从句(that 通常可以省略)
　　例如：
　　I heard that be joined the army.

　　(3) 动词+间接宾语+宾语从句
　　例如：
　　She told me that she would accept my invitation.

　　2. 作介词的宾语。
　　例如：
　　Our success depends upon how well we can cooperate with one another.

　　3. 作形容词的宾语。
　　例如：
　　I am afraid (that) I’ve made a mistake.
　　That 引导的从句常跟在下列形容词后作宾语：
　　Anxious， aware， certain， confident， convinced， determined， glad， proud， surprised， worried， sorry， thankful， ashamed， disappointed， annoyed， pleased， hurt， satisfied， content 等。也可以将此类词后的that 从句的看作原因状语从句。

　　4. It 可以作为形式宾语。
　　It 不仅可以作为形式主语，还可以作为形式宾语而真正的宾语that 从句则放在句尾，特别是在带复合宾语的句子中。
　　例如：
　　We heard it that she would get married next month..