问题补充：
Today Bob contradicted Ms. Li, our math teacher, in class, made her angry with him.
A. that
B. which
C. what
D. who
答案：
A. that
(答案→)B. which
C. what
D. who
解析：句意:今天鲍勃在课堂上反驳了李老师，这使她很生气。这里是定语从句，先行词是逗号前面的句子，关系词在从句中作主语，that不能引导非限制性定语从句，what不能定语从句，who的先行词必须是人，故选B。
