1、He liked the people whom he lived with.whom只能代替宾语。

2、He liked the people with whom he lived. 把with 和 whom 连起来，加上he lived,放在一起修饰the people。

3、注：介词若是和连接词放在一起的定语从句，只能是修饰物用which，修饰人用whom。不能用that，who这两个连接词。也不能省略。定语从句与主句间可以加逗号。