1.is covered with
2.received a letter from
3.was ready to
4.Which one
5.不懂（句子有问题？）
6.found guangzhou is a modern city
7.so heavy that the little boy can not carry it.
复合句：
主从复合句
主从复合句由一个或一个以上的从句构成,主句为句子的主体,从句不能独立,只用作句子的一个成分.
主从复合句主要包含定语从句,状语从句和名词性从句.
定语从句
定语从句的主要内容如下：
一、定语从句的定义及其结构
二、关系代词和关系副词在定语从句中的作用
三、关系代词引导的定语从句
四、关系副词引导的定语从句
五、关系代词前带介词的定语从句
六、由关系代词as引导的定语从句
七、关系代词that 与which 用法的区别
八、限制性定语从句与非限制性定语从句的区别
一、 定语从句的定义及其结构
定语从句的定义:
1.定义：在复合句中，修饰某一名词或代词的从句叫定语从句。例如：
The girl who is standing there is Mary.
先行词 关系词
2.先行词：被定语从句所修饰的词。
关系词：引导定语从句的词。
应该注意的是：
a.定语从句一般位于先行词之后，由关系代词或关系副词来引导。
b.当关系代词作定语从句的主语时，其后的谓语动词的人称和数取决于先行词。
c.关系代词和关系副词在定语从句中担任某一成分。
二、关系代词和关系副词在定语从句中的作用
关系词 先行词所指 关系词在句中作用
关系代词 that 人/物 主、宾、
which 物 主、宾、
who 人 主、宾
whom 人 宾
whose 人/物 定
as 人/物/事情 主、宾、
关系
副词 when 时间 时间状语
where 地点 地点状语
why 原因 原因状语
引导定语从句的有关系代词who, whom, whose, which, that 和关系副词 when, where 等。
关系代词和关系副词用来引导定语从句，在先行词和定语从句之间起纽带作用，使二者联系起来。关系代词可作主语，宾语，和定语，关系副词可作状语。
1． 关系代词在定语从句中作主语：
关系代词在定语从句中做主语时，从句中的谓语动词的人称和数必须和先行词一致。
例如：
There is somebody who wants to see you.
The novel which was written by Tom is very interesting.
I like pictures that are painted by my students.
以上三句中的关系代词 who, which, that 在从句中均作主语。
第一例中的定语从句的谓语动词wants和先行词somebody的人称和数相一致。
第二例中的定语从句的谓语动词was和先行词novel的人称和数相一致。
第三例中的定语从句的谓语动词are和先行词pictures的人称和数相一致。
2. 关系代词在定语从句中作宾语
The new student whom I want to introduce to you has come.
The letter that (which) I received yesterday was from a friend of mine.
在口语和非正式文体中，定语从句中关系代词可以省略
3。 关系代词在定语从句中作定语
This is the student whose pronunciation is excellent.
The book whose cover has come off is mine.
4。 关系代词在定语从句中作状语：
关系代词where, when 在定语从句中分别作地点状语和时间状语
The doctors came at a time when we need them most.
Later, man began to settle in the places where the food and water were plentiful.
二、 关系代词引导的定语从句
who指人，在定语从句中做主语，例如：
That’s the teacher who teaches us Chinese.
Whom指人，在从句中做宾语，口语中who可以代替whom，在限制性定语从句中也可以被省去，但作介词宾语时只能用whom，例如：
Do you know the worker (whom) we met at the school gate?
whose指人，也可以指物，在从句中做定语，例如：
The professor whose wife teaches you English has been to China.
The house whose windows were damaged has now been repaired.
Which指物，在定语从句中做主语或宾语，which充当宾语时，在限制性定语从句中也可以被省去，例如：
Here is the book which the teacher mentioned yesterday.
The book which is on the desk is a dictionary.
关系代词which 的先行词在作非限制性定语从句中有时不是一个单词，而是前面整个主句所表达的概念，例如：
The foreign teacher helped us with spoken English, which was very kind of her.
that 多指物，也可指人，在从句中做主语或宾语。指物时，其用法和which大致相同。
This is the power station that (which) we built last year.
Who is the person that is playing the piano?
四、 关系副词引导的定语从句
when指时间，在定语从句中作时间状语，
例如：we’ll never forget the day when the People’s Republic of China was founded.
Where 指地点，在定语从句中作地点状语，例如：
This is the place where I was born.
六、 关系代词前带介词的定语从句
关系代词与介词
关系代词whom，which 在定语从句中作介词宾语时，介词可放在whom, which之前，也可以放在句中原来的位置上，例如：
Is he the man (whom) you spoke to yesterday?
该句的介词to 放在原来的位置上，whom 可以省略。
Is he the man to whom you spoke yesterday?
该句的介词to 也可以放在whom之前，whom 不可以省略。
含有介词的短语动词等固定词组一般不可以分开，例如：
This is the answer which we are looking for .
注意： 关系代词作介词宾语时，介词不可以放在that 之前，例如：
Can you lend me the book that you talked about the other day?
介词about 不可以放在关系代词that 之前。
引导定语从句的关系副词when, where和关系代词 whose 有时可以用“介词+which” 来代替，例如：
We’ll never forget the day when (on which) the People’s Republic of China was founded.
This is the place where (in which) I was born.
The book whose cover has come off is mine.
The book, the cover of which has come off is mine.
六、由关系代词as引导的定语从句
As 可作为关系代词来引导定语从句，例如：
He is from Beijing, as you know.
在这里，as 引导的非限制性定语从句，相当于which引导的非限制性定语从句
He is from Beijing, which you know.
但as引导的非限制性定语从句可以放在句首，而which引导的非限制性定语从句不能放在句首。
As you know , he is from Beijing.
As 可作为关系代词来引导定语从句，既可以单独引出定语从句，又可以与主句中的the same 或 such 相呼应，从句中的谓语动词常省略，例如：
She is the same age as you (are).
I hope to get such a dictionary as he is using.
七、 关系代词that 与which 用法的区别
which 可以引导一个非限制性定语从句，that 则不能，例如：
He had failed in the English, which made his father very angry.
Which 之前可以有介词，that 之前则不能，例如：
This is the house in which Tom used to live.
只能用that，而不能用 which 的情况
1.当先行词是all, everything, nothing, something, anything, much, little, few，none 等不定代词时，例如：
That is all that I want to say.
2. 当先行词被序数词或形容词最高级所修饰时，例如：
The first place that I visited in Beijing was the Great Wall.
This is the best film that I have ever seen.
3. 当先行词被 the very,the only,the just 等词修饰时，例如：
Mr. Smith is the only foreigner that he knows.
4. 当两个先行词一个指人,一个指物时，例如：
The famous writer and his works that the radio broadcast have aroused great interest among the students.
5. 当主句已有疑问词who或which时，例如：
Who that you have even seen can do better?
6. 如果有两个定语从句，其中一句的关系代词是 which ，另一句则用that，例如：
Let me show you the book that I borrowed from the library which
was newly open to us.
八、 限制性定语从句与非限制性定语从句的区别
定语从句分限制性定语从句与非限制性定语从句两种，限制性定语从句为先行词不可缺少的定语从句，如果将这种定语从句省去，主句的意思就会不完整或不明确。这种定语从句和主句的关系十分密切，不用逗号分开，例如：
She is the nurse who looks after the children.
非限制性定语从句只是对先行词的附加说明，如果将这种定语从句省去，也不至于影响主句的意思，它和主句之间通常用逗号分开，例如：
The letter is from my brother, who is working in the factory.
请比较以下限制性定语从句与非限制性定语从句在意义上的区别：
All the books there, which have pictures in them, were written by him.
这儿所有的书都是他写的。书里面都有插图。
（ 该句为非限制性定语从句，“书里面都有插图”只是对先行词的附加说明）
All the books there which have pictures in them were written by him.
这儿所有里面有插图的书都是他写的。
（ 该句为限制性定语从句，意即书里面没有插图的书不是他写的）
参考资料：http://zhidao.baidu.com/question/1304224.html