case 后接定语从句为何不用WHICH

in which case定语从句用法不明白，which为什么能代替一句话，把原句换which不符~

which是关系代词，用来代替前面的先行词或一句话，这是语法规定，没有为什么！

1.先行词是all, any, everything, anything, nothing ,something, much, little, few, none ,the one 等时① There is much that should be used.

② You can take any seat that is free.
2.先行词被all, any , no, only, little, much, very, every, some, few, none 等修饰时① I have read all the books (that) you gave me.

② Every dictionary that our library bought is good.
3. 当先行词前有形容词的最高级修饰时① This is the most interesting book that I have ever read.
4. 先行词前有序数词修饰时,包括 the last.① The first lesson that I learned will never be forgotten.

② The Great Wall is the last place that Mr. Smith is going to visit before he leaves Beijing.

5. 在以 which, who作主语的特殊疑问句中的定语从句中① Who is the man that is reading a book there?

② Which is the magazine that you borrowed from the reading room?
6.当先行词既有表示人又有表示物的词时① We talked of the things and persons that we remembered.

7. 当先行词在定语从句中做表语时,无论先行词是人还是物① China is no longer the country that she was.

8.主句以there be 开头时① There is little that I can do to make up for the lost time

where=in which
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像case，situation，scene，point，activity等词语如果表示的是【在这种情况里】
定语从句的引导词就要使用where
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当然如果表示的不是在这种情况里面，就不能使用where
比如说
there is one point that we must insist on

“有兴趣可以关注一下我们的英语人工翻译队”

应该用in which 。我是这样理解的：在这样......的场合中。

case---in the case， 还原定语从句时，句子中会缺少介词in，而where=in which，