突发公共卫生事件是指突然发生，造成或者可能造成社会公众健康严重损害的重大( )A．

Over the past two years, a firm reported higher operating cash flow as a result of securitizing its accounts receivable and from increasing income tax benefits from employee stock options. The tax benefits are solely the result of higher tax rates. Should an analyst conclude that these two sources of operating cash flow are sustainable()

A. Both sources are sustainable.

B. Neither source is sustainable.

C. Only one of these sources is sustainable.

在特定波长的紫外光下可以看到第五套人民币纸张中有不规则分布的红色和绿色荧光纤维。

水泵运行过程中，会造成叶轮前后盘上的压力不平衡，前盘上的压力（）后盘上的压力。

A.大于

B.小于

C.等于

大板房的纵、横墙板交接处的竖向接缝应符合规范规定采用现浇混凝土灌缝，灌缝应用细石混凝土，其强度等级不应低于（），同时不低于墙板混凝土的强度等级。

A.C10

B.C15

C.C20

D.C30

目前国内电厂使用的盘车，分类如何？