加工表面不平度的波距L和波高H的比值小于50时(即L/H50),称为()
A、宏观几何形状误差;
B、表面波度;
C、表面粗糙度;
参考答案:C
By the time Fred gets back home, his girlfriend for London to study.
A.will have left
B.leaves
C.has left
D.will leave
属于传染性非典型肺炎氧疗的指征是()
A.体温超过38.5℃
B.X线胸片显示有明显吸收
C.有严重中毒症状,高热持续3天不退
D.频繁咳嗽、血丝痰
E.呼吸困难,气促