who可以引导名词性从句，它是疑问代词，意思是“谁”，后面引导的从句用陈述句的语序，如：
No one knows who cheated in the exam.
Do you know who broke the antique vase?
who或whom只有在一些特殊句型里，才作缩合连接代词使用，如：
Who breaks pays.
She could marry whom she likes.
Who is not for us is against us.
希望我能帮助你解疑释惑。
