一、that都可以引导什么从句？
答：1、用作
关系代词，引导定语从句
The only thing that I can do is to have a rest . 我唯一能做的事就是休息。
2、用作
关联词，引导
名词性从句That the earth turns around the sun is known to all. 地球围着太阳转这一点是众所周知的。（引导
主语从句）
It so happens that I know the man. 碰巧我认识那人。（主语从句）
I will see to it that everything is ready. 我会注意把一切准备妥当的。(
宾语从句)
The trouble is that we are short of money.困难就在于我们缺钱。（
表语从句）
There is no doubt that he is the best choice for this position. 无疑，他是这一职位的最佳人选。（
同位语从句）
3、构成短语，引导状语从句
Bring it nearer so that I may see it better .拿近一点，好让我看清楚些。 ( so that 引导
目的状语从句)
She got up early , so that she caught the early bus. 她起的早，所以赶上了早班车。( so that 引导
结果状语从句)
In order that everybody should hear him , he spoke loudly. 他大声说话，为了使大家都能听得见。（in order that引导目的状语从句）
Now that they have taken matters into their hands the pace of events has quickened.他们既然已着手自己来处理问题，事态的进展也就加快了。（now that 引导
原因状语从句）
（一）关系代词which的使用场合
1．如果
先行词是that，关系代词应用 which。如：
What was that which you said about him ？
2．先行词和定语从句之间被其它较长的成分分隔，用which较好。如：
I have some interests outside my professional work which gives me great pleasure．
3．一个句子中如有两个定语从句，一个定语从句用了关系代词that，另一个从句宜用which。如：
This is the book that you bought which you have lost．（第二个定语从句的先行词实际上是前一个定语从句的关系代词that）
I'll borrow a book which tells about the heroic deeds that the PLA did in the battles against the invaders．
但在平行结构中，应重复同一个关系代词。如：
I have a house which is located on the hillside，which faces the south．
4．
非限制性定语从句中关系代词一般要用which。如：
I will buy a book，which tells about the use of English idioms．
5．相当于
并列句和状语从句的定语从句，用which引导。如：
1）We went to the nearest port which we reached safely．
2）He persisted in having a bicycle which he actually had no use for．
6．关系代词前如有介词，关系代词要用 which。如：
They had a meeting at which he spoke on the current economic situation．
如把介词移至句末，可用that（或省略）。如：
This is the book（that）she was looking for．
（二）关系代词that的使用场合
1．一般说来，先行词是all，anything，everything，nothing，much，little，few等，关系代词应用that。如：
1）That's all（that）I know．
2）Everything that can be done is done．
2．先行词之前有all，any，every，no，little，much，only，very等修饰时，关系代词应用that。如：
1）He'll read all the books that are sold here．
2）Ask any questions（that）you don't understand．
3．先行词前有序
数词或形容词最高级修饰时，关系代词应用that。如：
1）This is the most wonderful film that I have ever seen．
2）The first thing that you should do is to work out a plan．
4．当先行词是to be的表语，或关系代词本身是从句的表语时，关系代词应用that。如：
1）It's a song that is very popular．
2）My hometown is no longer the place that it used to be．
5．当主句以There be开头时，关系代词应用that。如：
There is a seat in the corner that is still free．
6．当一个句子中含有两个定语从句时，如前一个已用关系代词which，后一个关系代词宜用that。如：
I'll borrow a book which tells about the heroic deeds that the PLA did in the battles against the invaders．
但两个定语从句的结构如果平行，一个定语从句中用关系代词that，另一个定语从句也应重复that。如：
He told me to read a book that is very short，and that is very interesting．
7．与the same（指同一物）连用，构成the same．．．that．．．结构时，关系代词只能用that。如：
This is the same museum that you once visited．
注意：the same．．．that．．．结构中的that不能用as代替，因为the same．．．as．．．与the same．．．that．．．的含义不同。
that可引导名词性从句，包括主语从句、宾语从句、表语从句，在句中作
从属连词，不引导状语从句，但in order that,so that可引导状语从句。
此句中，that作为同位语从句引导词来解释conclusion，与定语从句中的that相鉴别，定语从句中的that可以省略，而同位语中的that不可以。