There are two sales divisions, one of ____ are under the Line Di

There are two sales divisions, one of ____ are under the Line Director, Mr.Smith.
A、whom
B、which
C、that
D、them
【正确答案】：A
【题目解析】：one of____are under the Line Director,Mr.Smith 为非限制性定语从句，排除DC。先行词为人，且在介词之后，要使用宾格形式，whom，因此A正确。