当who做关系词时.只能从句中当主语吗

问题描述:

当who做关系词时.只能从句中当主语吗

He is the man who talked with me just now.
He is the man who/whom I talked with just now.
既可以做主语又可以作宾语的.
不过
He is the man with whom I talked just now.
如果把介词放在关系词前面的时候,就不能用who了.只能用宾格whom