Professor Li is the person to you should write.A. whomB. whoC. whichD. whose

问题补充：

Professor Li is the person to you should write.

A. whom

B. who

C. which

D. whose

答案：

(答案→)A. whom

B. who

C. which

D. whose

解析：本题的含义是李教授是你应该给他写信的那个人，修饰名词person是一个定语从句，现行词是表示人，关系词在从句中做介词的宾语，故关系词只能用whom，故本题选A。