英语定语从句只能用that的情况当先行词为主语表语或关系代词为从句表语时,必须使用that做引导词吗?比如说This is the book which he asks for.这样用可以吗?还是必须用This is the book that he asks for.另

英语定语从句只能用that的情况
当先行词为主语表语或关系代词为从句表语时,必须使用that做引导词吗?
比如说This is the book which he asks for.这样用可以吗?还是必须用This is the book that he asks for.
另外,还有个问题This is the book for which he asks.可以这么用吗?
这里因为有for,要用which；但是因为先行词作表语,又要用that.怎么办
回答时请把我的问题看完整 而且逐个回答 自己也不明白的就别来误导大家了

上面的回答各有各的优点,不过我比较倾向于 追风少年zzz 的回答~pipilu16888 的应试能力挺不错~
没有强性规定说“当先行词为主语表语或关系代词为从句表语时,必须使用that做引导词”,只是这种情况倾向于用that,但并不绝对.所以你最后那个句子并不矛盾.
This is the book which he asks for.
This is the book that he asks for.
上面两个句子都可以,还可以把which和that都省略.不过一般比较倾向于使用that或省略.
This is the book for which he asks.
只能用which,因为前面有for.介词后用which是条硬性规定.而不用that理由前面已解释~

要记住怎么用that和which,最简便的方法就是：
在逗号后面，和介词后面不能用that,其余尽量用that。
所以，第一句必须用This is the book that he asks for.
第二句，用This is the book for which he asks.
因为有介词for，就要要用which。

英语语法定语从句：只能用that引导的十三种情况
1.在there + be 的句型中，句子的主语是先行词，而且又是物。
例如：
There are two novels that I want to read. 我要读的有两本小说。
There is no work that can be done now. 没有什么工作现在能做的了。
2.当先行...

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英语语法定语从句：只能用that引导的十三种情况
1.在there + be 的句型中，句子的主语是先行词，而且又是物。
例如：
There are two novels that I want to read. 我要读的有两本小说。
There is no work that can be done now. 没有什么工作现在能做的了。
2.当先行词为主句的表语或者关系代词为从句的表语时。
例如：
This is the book that was bought yesterday.这就是昨天买的书。
Our school is no longer the school that it used to be. 我们的学校不再是以前的学校了。
3.以Here is (are)开头的句子时。
例如：
Here is a film that will move anyone.这是一部将使任何人受感动的电影。
Here are two books that I will buy.这是我要买的两本书。
4.It is (high)time +定语从句中。
例如：
It is time that we should have a rest.我们应该休息了。
It is high time that they started out. 他们该动身了。
5.当先行词是way等词时，关系代词用that或者in which在定语从句中作方式状语时，在口语中，常可省略。
例如：
This is the way that my father did this work.这就是我父亲做此工作的方式。
She admired the way in which I answered the questions. 她羡慕我回答问题的方式。
6.在双重限定性定语从句中，如果一个从句用who或者which引导时，那么另一个从句用that引导。
例如：
He is the student that I have ever see who can jump highest.他是我曾经看到过跳得最高的学生。
My brother studies in the school which is the most beautiful in our city that isn't far from here. 我的弟弟在我们的城市最美丽的学校读书，并且离这儿不远。
7.当先行词被the last , the very 和the only修饰时。
例如：
This is the very pen that I am looking for. 这正是我找的钢笔。
The only book I want to read is missing. 我唯一想看的书不见了。
8.在强调句子中，并且以who ,which, what开头时。
例如：
Who was it that was lost ? 究竟是谁迷路了？（此句中，最好不用who来代替that，避免重复。）
What was it that you did last week? 你上周究竟做什么了？
9.当先行词有序数词时。
例如：
You are the first person that I want to ask for.你是我要见的第一个人。
This is the second book that I have ever written.这是我写的第二本书。
10.当先行词被all, every, no , some, few , little, much, both等修饰时，
例如：
This is all that I want to say at the meeting.这就是我在会上要说的。
Have you any books that are worth reading? 你有值的看的书吗？
11.当先行词既指人又指物时。
例如：
The professor and his achievement that I heard about are admired by them .我听说的那位教授和他的成就得到他们的赞美。
Let's talk about the persons and the things that we can remember.让我们谈论能够想起的人和事。
12.当先行词为anything、everything、nothing时，关系代词用that,不用which；但用something时，用which或者that均可。
例如：
Everything we have seen in China is moving. 我们在中国看见的东西件件感人。
I have nothing that is worth reading. 我没有什么值得一读的东西。
13.当先行词是疑问代词who时。
例如：
Who that you have ever seen can beat him in chess? 你曾见过谁能在棋艺上打败他？
http://www.google.cn/search?client=aff-os-maxthon&forid=1&ie=utf-8&oe=utf-8&hl=zh-CN&q=%E8%8B%B1%E8%AF%AD%E5%AE%9A%E8%AF%AD%E4%BB%8E%E5%8F%A5%E5%8F%AA%E8%83%BD%E7%94%A8that%E7%9A%84%E6%83%85%E5%86%B5
祝你进步！

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必须用that有以下几种情况：
1，先行词既有人又有物
2，有限定性强的词，比如the only，the first
3，先行词是不定代词
this is the book————he asks for 这个空可以用which或that或不填
但一旦引导词前有介词，如for，就要用which