与填料密封相比，机械密封具有()的特点
A、密封性可靠
B、寿命长
C、摩擦消耗小
D、对旋转轴振动不敏感
参考答案：A,B,C,D
—I’m sorry I stepped on your foot; it was an accident.
—It wasn’t! You did it ______________ .
A．as usual
B．on purpose
C．at an end
D．right away
花儿
