链传动中小链的齿数对链传动的工作寿命影响很大,一般情况下对套筒流滚子链规定主动链轮的最少齿数Zmin=(),而最多齿数Zmax=120。
A.5
B.7
C.9
D.11
参考答案:C
She devotes herself _______________ , and makes it her life. [ ]
A. to teach
B. to teaching
C. teach
D. teaching
脉冲后沿的下降时间是()所需时间确定的。
A.0.5Vm下降到0.1Vm
B.0.1Vm上升到0.9Vm
C.0.9Vm下降到0.5Vm
D.0.9Vm下降到0.1Vm