用that不用which的情况 先行词是all，much，few，little，everything，anything，nothing，none，the one等不定代词时 先行词被all，few，little，much，every，some，no等词修饰或被the only，the very，the same，the last等限定词修饰时 先行词是形容词的最高级或序数词或先行词被其修饰时 先行词既指人又指物时 主句是who或which等引导的特殊疑问句时 用which不用that的情况 在非限制性定语从句中用which不用that 介词后边用which不用that 　　We should do everything that is useful to the people.

　　我们应该做一切有益于人民的事。

　　This is the smallest computer that can be found in the world now.

　　这是目前发现的世界上最小的计算机。

　　I bought a great many books，on which I spent all my money that I saved.

　　我买了很多书，这些书花了我积攒的所有的钱。

　　[即时训练1]

　　单句语法填空

　　①Happiness and success often come to those who are good at recognizing their own strengths.

　　②Do you know the reason why he was absent yesterday?

　　③As is often the case with children，Amy was better by the time the doctor arrived.

　　④We live in an age when more information is available with greater ease than ever before.

　　二、"介词＋关系代词"的用法

　　1．"介词＋关系代词"结构中介词的确定方法。

　　(1)根据从句中的谓语动词或主要的形容词确定介词。

　　The poor man has no house in which he can live.

　　那个穷人没房子住。

　　(2)根据定语从句修饰的先行词确定介词。

　　I don't know the reason for which he was late for school.

　　我不知道他为何上学迟到。

　　(3)根据句子所要表达的意思确定介词。

　　This is the pilot by whom my son was saved.

这就是那位救了我儿子的飞行员。