Mary was much kinder to Jack than she was to the others of course made all the others u

问题补充：

Mary was much kinder to Jack than she was to the others,, of course, made all the others upset.

A. who

B. which

C. what

D. that

答案：

A. who

(答案→)B. which

C. what

D. that

解析：考查非限定性定语从句。逗号后的非限定性定语从句中缺少主语，选择which。