轮对在轨道上滚动时钢轨对轮对的切向反作用力称为（）
A.制动力
B.摩擦力
C.制动压力
D.粘着力
参考答案：D
Peter hardly had time for concerts at that time, ________? [ ]
A. wasn't he
B. was he
C. didn't he
D. did he
最基本、最主要的考核形式是( )
A．平时考核 B．晋升考察C．领导人员主持考核工作 D．定性考核
