英语中宾语从句中who，whom的区别

简单的说whom是who的宾语形式，whom前可以有动词和介词，现代英语中who可替代whom

限制性定语从句

关系代词that/which, who/whom/whose
a.必须用that情况(略)
b.必须用which情况(略)
c.定语从句的谓语须与先行词保持一致
e.g. I, who am your friend, can understand you.
The books which lie on the desk are mine.
He is one of the students who were present.
He is the only one of the students who was present .
d.关系代词的省略
1)作及物动词或介词的宾语,作表语.
e.g. He is all (that )a teacher should be.
2).如果句首或句尾是there is ,here is ,that is, it is时,用作主语的关系代词可以省略，这种情况主要用于口语中.
e.g. Who was it (that )said so?
Here issomebody (that)wants to see you.
That is the best dictionary (that)there is in this library.
There is a man downstairs(who) wants to see you.
3)非限制性定语从句who ,whom, which, whose等不能省略
e.g .My brother ,who isa teacher, can speak German.
Mr. A, whom you know ,is the tallest in our class.
The weather turned out to be very good, which was more than we could expe