Mary was always singing high praise for her role in the office, ，of course,made her colleagues unhappy.
A. who
B. which
C. this
D. what
网友回答
A. who
(答案→)B. which
C. this
D. what
解析：填空处是指前面整个句子所述的内容，为非限制性定语从句，用which引导。句意为“玛丽总在赞扬她在办公室里的作用，这当然使她的同事们不高兴了”。