1.主语从句
例句：The person gave me a free ride is the lorry driver.
1）句子本身没有语法错误,但是这不是主语从句,只要把它化简分析就可以一目了然：
* 句子的主要成分：The person is the lorry driver.主系表结构.
* 过去分词短语 gave me a free ride 是 the person 的后置定语,也可以改为定语从句：(the person) who gave me a free ride ,意思是“让我免费乘坐的（那个人）”.
2）所谓主语从句指的是用句子作主语,或者是把主语扩展成一个句子,引导主语从句有四种情况：
that 从句 —— 用来陈述一个事实,如：
* That the person gave me a free ride / is known to you.那个人让我免费乘坐这件事你已经知道.
wh- 从句：陈述已知的具体问题,如：
* How the person gave me a free ride / is known to you.那个人怎么让我免费乘坐你已经知道.
if/whether 从句：陈述未知的或然问题,如：
* If/whether the person gave me a free ride / was still not known.那个人是否让我免费乘坐还是个未知数.
关系代词型从句：表示“所...的（东西、事情、话等）”
* What he said / was not quite right.他所说的不完全正确.
另外前三种从句都可以用形式主语 it 改写：
* It is known to you / that the person gave me a free ride.
* It is known to you / how the person gave me a free ride.
* It is known to you / whether/if the person gave me a free ride.
2.宾语从句
例句：I heard that a lorry driver gave you a free ride.
这是一个标准的宾语从句.除 that 引导外,也可以用上述的其它三种引导.
3.表语从句
例句：The lorry driver is who gave me a free ride.
这个句子在语法表面很像一个表语从句,但是意思上却说不通.
这类从句的主语只能用表示事情的名词充当,不能用具体的人或东西.举例如下：
* The news I heard is / that the lorry driver gave him a free ride.我听到的消息时达车司机让他免费乘坐汽车.
* The question is / when the lorry driver will give me a free ride.问题是卡车司机什么时候让我免费乘坐.
* My doubt is / if the lorry driver will give me a free ride.我的疑虑是卡车司机是否会让我免费乘坐.
4.同位语从句
例句：I heard the story that a lorry driver gave you a free ride.
正确.
归纳：以上的从句统称为名词从句,名词从句有四种类型（已经在主语从句做过介绍）.
1）that 从句；
2）wh-从句（包括when,where,why,who,which 和 how）；
3）if/whether从句；
4）关系代词性从句（包括what/whatever——所...的东西、事情、话等；where/wherever——所...的地方；when/whenever——所...的时间；）
5.定语从句
例句：This is the lorry driver who gave me a free ride.
正确.
6.状语从句
例句：I thanked the lorry driver because he gave me a free ride.（原因状语）
正确.