This is the question about which we've had so much discussion
这句话中为什么要有个介词about?
Everything that he said seemed quite reasonable
这句话中为什么又没有介词了?
介词什么时候,用什么时候不用??
This is the question about which we've had so much discussion
这句话中为什么要有个介词about?
【答】about which we've had so much discussion 是定语从句,question 是定语从句修饰的先行词。Have ...discussion about / on ... 表示“就......进行讨论”,所以要有个介词about或者 on 。
Everything that he said seemed quite reasonable
这句话中为什么又没有介词了?
【答】这里的 that he said 是定语从句,修饰Everything。Everything是主句的主语, seemed 是系动词, quite 是程度副词,修饰作表语的形容词reasonable。所以,不能用介词。