实在搞不懂whom什么时候用,书上说做宾语的时候用,我还是不太明白.举个例子就最好了

whom就是who的宾格,就是whom在从句中作宾语时就用whom,比如说
He is the man whom I turn to for help.其实就是I turn to whom for help.
同理,在从句中作介词的宾语其实就是正常语序下的介宾结构啊,就说上面这句话,to是介词,whom和to构成介宾短语,in which也是这个道理,比如说 this room is the one where（in which） I ever lived .正常语序肯定是live in the room,所以用which是对room提问,用where就是对in the room 提问了.

关系代词引导的定语从句
1.who指人在从句中做主语
(1) The boys who are playing football are from Class One. 在踢足球的男孩们是一班的.
(2) Yesterday I helped an old man who lost his way. 昨天，我帮助了一个迷路的老人.
2. whom指人...

whom现在很少用了 全部可以用who代替
Whom 出现在从句里面时，所有用whom的地方都可以用who代替。Whom 这个词只出现在很正式的书面语。口语不用。
2． Whom 在介词（如 to, from, at, of..）后面时，不可替换。
Who told you the story? （主语）
Who is that man over there...