who在引导宾语从句时可以在从句中做主语，也可以代替whom做宾语表语。因此会出现两种情况。当作主语时是who is当做宾语表语时是who he is.
I don\'t know who is his dad.
I don\'t know who he is.
I don\'t know who loves him.
I don\'t know whom(who) he loves.
水利万物而不争,
而万物莫能与之争。
