对柱塞偶件及出油阀偶件进行（）试验、滑动性试验时，对磨损严重（泄漏严重）的偶件应予以更换。
A.密封性
B.常规性
C.开放性
D.封闭性
参考答案：A
It is clear that the whole world is passing through a social revolution in which a central ________
must be taken by scientists and technologies.[ ]
A．process
B．action
C．part
D．measure
( )与税收收入的表现恰好相反。
A．最终消费B．平滑支出C．转移支付D．正向税收
