阅读和分析数控机床电气原理图时，首先要分析( )。
A．伺服驱动装置
B．数控装置
C．测量反馈装置
D．联锁与保护环节
参考答案：B
用方框中所词组的正确形式填空。每词只用一次。
laugh, tooth, little, serious, minute
小题1:Lisa is _______ of us. She hardly ever smiles.
小题2:The bus ride usually takes us about 25_____ to get to school?
小题3:My baby brother has three _______ . He is too young to eat anything.
小题4:We must try to eat_______ meat. Too much meat is bad for our health.
小题5:He is very funny. He always makes his classmates _____.
木块在大小为5N的水平拉力作用下，10s内在水平面上沿拉力方向前进2m，拉力做功为______J，功率为______W；若木块重15N，在此过程中重力对木块做功为______J．
