1. 当先行词是不定代词或被它们修饰时。
Is there anything that I can do for you 有什么要我做的吗 All that can be done must be done. 凡是能做的事情都必须做。
He answered few questions that the teacher asked. 他几乎没有回答老师的那些问题。
2. 当先行词被形容词最高级或序数词修饰时。
This is one of the most interesting books that were sold in this bookstore. 这是这家书店售出的最有趣的书之一。
The first thing that should be done is to get some food. 该做的第一件事是弄点吃的。
3. 当先行词有the very, the only, the same等词语修饰时。
That’s the only thing that we can do now. 目前我们只能这样了。
Those are the very words that he used. 那就是他的原话。
4. 当先行词是一个既指人又指物的词组时。
They were talking about the persons and things that they saw in the factory. 他们在谈论在工厂里看到的人和事。
5. 当关系代词在定语从句中作表语时。
China is not the country that it was. 中国已经不再是过去的中国了。
6. 当要避免和疑问词which重复时。
Which is the car that was made in Shanghai 哪辆车是上海制造的 2. 关系副词引导的定语从句 1．关系副词when在句中作状语，表示时间。
It happened on the day when I came back from Guangzhou. 这件事发生在我从广州回来的那一天。
2．关系副词where在句中作状语，表示地点。
This is the room where Lu Xun once lived. 这是鲁迅曾经住过的房子。
这里的关系副词where可以用in which替换。
3．关系副词why在句中作状语，表示原因。
Do you know the reason why we left here 你知道我们离开这儿的原因吗