1.who whom
who在从句中可以作主语或宾语,whom只能作宾语.
eg.1.the girl who（作主语）came this morning was my sister.
2.the girl who/whom（作宾语）you met this morning was my sister.
*介词后只能加whom,如 to whom(是介词后紧跟,中按没有别的词）
eg.The girl to whom you talked this morning was my sister.
2.which 一般指代物,或主句的整个内容 that 可指代人或物
前面有介词时只能用which.
eg.1.This is the cafe in which I first met him.
2.this is the cafe that I first met him in.
*.1.前面有逗号时,后面不能用that（指紧跟逗号）,只能用which.
eg.He drove too fast,which was danderous.
2.先行词是不定代词,主句中有序数词,先行词由theonly, the same, the last 等修饰时,先行词是两个或是两个以上的词,分别表示人和物时,或主句是who,which等开头的特殊以文具,以及先行词被形容词最高级修饰时,都只能使用that.
3.where
where是一个副词,所以用了where,就不需要使用介词.
eg.1.This is the city where I live.
2.This is the city which I live in.
3.This is the city in which I live.
我讲得挺乱的,不知道你看得懂么?
