奖励和惩罚都是控制的手段。
参考答案：对
Betty and John have come back , but ______ students in the class aren't here yet. [ ]
A. the other
B. others
C. another
D. the others
割缝衬管直缝的缝长一般为（）。
A、25～50mm
B、50～300mm
C、300～400mm
D、400～500mm
