介词提前时，定语从句的引导词只能用 which, whom, whose,而不能用that或who。在判断使用什么样的介词时，一要看句意；二要看搭配关系，即看后面的谓语动词和前面被定语从句修饰的名词以确定应搭配什么样的介词。介词提前有以下几种情况： ［误］ The clever boy made a hole in the wall, in which he could see what was happening inside the house。
［正］ The clever boy made a hole in the wall, through which he could see what was happening inside the house。 ［析］从句意和介词跟名词的搭配上看，定语从句引导词应用表示"从……中间穿过"之意的介词through。
［误］ There were two things of which they took pride。 ［正］ There were two things in which they took pride。 ［析］take pride in=be proud of。
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答：简单的说: that在主语为人或物都可以使用,which要在主语为人是才可以使用详情>>
