Is this the reason why (for which) he quit the job?

这是他辞职的理由吗？

2．"from where"结构，也可以引导定语从句。

We stood at the top of the hill，from where we could see the town.

我们站在山顶上，从那里我们能看见那个城镇。

四、限制性定语从句只能用that的几种情况

1．如果先行词是all，much，little，anything，something，nothing，everything，none，some等不定代词时，关系代词一般只用that，不用which。

Is there anything that I can do for you?

我能为你做些什么吗？

2．如果先行词被the only，the very，the right，the same，the last，the best等词修饰时，关系代词常用that(指人时，还可以用who)。

This is the very book that I want to find.

这就是我想找的那本书。

That is the best film that we have seen.

那是我们看过的最好的电影。

I was the only person in my office that/who was invited.

我是我们办公室唯一被邀请的人。

3．当先行词被all，every，no，some，any，little，much修饰时。

All the people that are present burst into tears.

在场的所有人都哭了。

You can take any seat that is free.

你可以坐任何空着的座位。

4．当先行词是序数词或形容词最高级或被序数词或形容词最高级修饰时。

When people talk about Hangzhou，the first that comes to mind is the West Lake.

当人们谈及杭州时，第一个想到的就是西湖。

It is the first foreign book that I have ever seen.

这是我看过的第一本外文书。

This is the most beautiful flower that I have seen.

这是我见过的最美的花。

5．在there be句型中，常用that。

There is a man that lives in that village.

在那个村庄里住着一个人。

6．先行词既有人又有物时，关系代词用that。

The boy and the dog that are in the picture are very lovely.图画中的小男孩和小狗非常可爱。