一.用that不用which
1）先行詞是最高級或他前面有形容詞最高級時
This is the best--that--has been used against air pollution in cities.
English is the most difficult subject --that-- you will learn during these days.
2)先行詞是序數(shù)詞或它前面有一個序數(shù)詞時
He is the last person--that-- i want to see.
3)主句中有疑問句
Which is the pen --that-- you lost?
4)先行詞既有人又有物時
The bike and its rider --that--had run over an old man were taken to the police station.
5)先行詞是 all, much, little ,something,everything,anything,nothing,the one時
6）先行詞前有 only,any,few,little,no ,all,one of,the same, the very等詞裝飾時
7）有2個定語從句,其中一個關(guān)系代詞已用which,另一個應用that.
Tom built up a factory which produced things that had never been seen before.
二.用which不用that：關(guān)系代詞前有介詞
This is the school in--which-- you will study.
.原句本來就有that
Let me show you the book--that-- i borrowed from the library--which-- was newly open.
哎,沒分的,打那么辛苦白干了...T-T