机械制动是水轮发电机组的一种（）制动方式。
A.唯一；
B.传统；
C.先进；
D.不常用；
参考答案：B
— Why is Mr. Li so happy this morning?
— Because he was honoured with a(n) _____ for excellence in teaching. [ ]
A. present
B. gift
C. award
D. reward
