例如：（注意关系代词在定语从句中所充当的成分）
① Do you know the professor who/that will give us a speech next week? （作主语）
② I read a report about his new novel that/ which will soon be published. （作主语）
③ The plan that/which they argued about was settled at last. （作宾语）
④ This is the new secretary (who/whom/that) I would like to introduce to you. （作宾语）
⑤ The soldier whose legs were badly wounded was operated on without delay. （作定语）
注意：关系代词在定语从句中充当宾语时可以省略，充当主语时则不能。（见上例③④）
（二）关系代词that代替which的一些情况
which, that 在代替物时，一般可以通用。
但在有些情况下，只用 that。
⑴ 先行词是最高级形容词或它的前面有最高级形容词修饰时。
例如：
