问题描述：
1.He has made a lot of promises,none of ( )carried out.2.He has three sisters,( )is a doctor.
1.A.them B.which
2.A.all of them B.all of whom C.none of whom
并分析不同之处
1.A.them B.which
2.A.all of them B.all of whom C.none of whom
并分析不同之处
问题解答：
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