4. That-从句作主语通常用it作先行词，而将that-从句置于句末，例如：

　It is quite clear that the whole project is doomed to failure.很清楚，整个计划注定要失败。

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

　用it作形式主语的that-从句有以下四种不同的搭配关系：

　 a. It + be + adj. + that从句

　　It is necessary that…　　 有必要……

　　It is important that…　　 重要的是……

　　It is obvious that…　　 很明显……

　 b. It + be + 过去分词 + that从句

　　It is believed that…　　　人们相信……

　　It is known to all that…　从所周知……

　　It has been decided that…　 已决定……

　 c. It + be + n. + that从句　　It is common knowledge that…　 ……是常识

　　It is a surprise that…　 令人惊奇的是……

　　It is a fact that…　　 事实是……

　 d. It + be + vi. + that从句

It appears that…　　　似乎……

It happens that…　　　碰巧……

It occurred to me that…　 我突然想起……

3. 当从句是由选择问句转化而成时，一定要用whether构成whether...or结构。

2. 主句和从句要保持时态上的一致性，从句还要保持陈述句语序。

1. 由从属连词that引导的从句叫做名词性that-从句。 That只起连接主句和从句的作用，在从句中不担任任何成分，本身也没有词义。名词性that-从句在句中能充当主语、宾语、表语、同位语

同位语从句中先行词不充当从句成分，从句是用来解释先行词的内容。That从句作同位语，that不能省略。

▲Word came that our football team had won the match. 消息传来，我们的足球队赢了比赛。

▲May I ask a question when the meeting will be held? 我能否问个问题，会议什么时候举行？

第二节 实战演练

宾语从句在句中作宾语，引导宾语从句的that可以省略。whether和if可互换，但介词宾语或有or not时，用whether.

▲They know that the habit may kill them. 他们知道这个习惯能使他们致死。

▲They doubt whether or not Jack is a good student. 他们怀疑Jack是否是一个好学生。

▲They wanted to see which shops offered the best advice and service. 他们想了解哪家店提出的建议和提供的服务最好。

表语从句在句中作表语，它位于主句的联系动词之后。that从句作表语，that不能省略。表语从句只用whether，不用if。

▲The problem is that smokers cannot go without smoking. 问题是抽烟的人不抽烟就会感到难受。

▲The question is whether it is worth doing. 问题是这是否值得做。

▲This is where he has worked for years. 这就是他多年工作的地方。

3. It作形式主语主要包括以下几种类型和搭配关系：

　 1)It + be + adj. + 从句 　　　　 It was obvious that the driver could not control his car. 　　　 2)It + be + n. + 从句 　　　　 It is a pity that he missed the lecture.

　 3)It + be + 过去分词 + 从句 　　　　 It is said that they have won the game.

　 4)It + be + vi. + 从句

　　 It seems that something is wrong with the computer.

2. 很多主语从句都可以用that作形式主语。例如：

It is very interesting that he likes such kind of books.

It remains a question whether he will be able to come.

1. 用作主语的从句叫主语从句。that从句作主语，that不能省略。

▲That he likes such kind of books is very interesting.他喜欢这种书是非常有趣的。 　　 ▲Whether he will be able to come remains a question. 他是否能够来仍然是一个问题。

▲What he is looking for is none of your business. 他在找什么与你无关。