1.当先行词是nothing, something, anything, all, each等不定代词时。
e.g. Do you have anything that is important to tell me?
2.当先行词被all, any, some, no, not, every, each等修饰时。
e.g. I have some books that are very good.
e.g. This is the first book that I bought myself.
The biggest bird that I caught is this bird.
e.g. Which is the bike that you lost?
Who is the woman that was praised at the meeting.
China is no longer the country that she was.
Edison built up a factory which produced things that had never been seen before.
He asked for the latest book (that) there is on the subject.
8.当先行词被the very, the last, the next, the only 等词修饰时。
e.g. This is the very book that I lost yesterday.
e.g. I won’t forget the things and the persons that I saw.
e.g. Mary has a book, which is very precious.
e.g. This is a house in which lives an old man.
e.g. That dog which I found in the street belongs to Mary.