Dorothy was always speaking highly of her role in the play of course made the others

问题补充：

Dorothy was always speaking highly of her role in the play, , of course, made the others unhappy.

A. who

B. which

C. this

D. what

答案：

A. who

(答案→)B. which

C. this

D. what

解析：

B。of course 为插入语，若将项其去掉，则答案显然是B。