常用的轴封有副叶轮密封、填料密封以及（）3种形式。
参考答案：机械密封
—That's not what life is about! You only have an eye for money.
—______ I've not changed towards you.[ ]
A. So what?
B. If so.
C. What if?
D. How come?
定位轴线的编号写端部的圆圈内，其直径为______。
A．7～9mm
B．10～12mm
C．8～10mm
D．12～14mm
