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。

2. 名词性wh-从句，即以wh-词连接的名词性从句。Wh-词包括：

　 连接代词：who, whom, whose, what, which, whoever, whatever, whichever

　 连接副词：when, where, how, why

连接词whether, if不充当句子的任何成分。