加紧力垂直于主要定位基准面，以保证工件（），变形小，从而提高加工精度。
A、转动灵活
B、加工方便
C、定位稳定
D、减小震动
参考答案：C
— I ____ to a party, but I’ve got nothing to wear.
— Why don’t you have a dress made for the party?
A．was asked
B．will ask
C．have asked
D．have been asked
在瓷横担上严禁挂梯作业
