电接点水位计测量筒必须垂直安装，筒体中点（零水位）必须与汽包机诫中心处于同一高度。
参考答案：错
—How long did Mary work here?
—For half a year, but she didn’t leave us much ____. We hardly remember what she is like.
A．expression
B．explanation
C．impression
D．conclusion
车削一锥度为1：5的圆锥孔，工艺规定留磨余量0.5～0.4mm，若用标准塞规测量，则塞规刻线中心离开工件距离是多少
