A. to who B. to whom C. whose to D. whom to
答案：D. whom to
这是“特殊疑问词+动词不定式”的结构，通常可以改为宾语从句，如：
He wants to know whom/who he should ask about Father Christmas.
He doesn't know what to do.=He doesn't know what he should to do.
I don't know when to start.=I don't know when I should/will start.
等等，很多。
当主句的宾语和从句的宾语一致时，也就是同一个人时，可以互相改写。
温馨提示：答案为网友推荐，仅供参考