()工件的磨削表面是由砂轮上大量磨粒刻划出无数极细的刻痕形成的,工件单位面积上通过的砂粒数越多,则刻痕越多,刻痕的等高性越好,表面粗糙度值越小。
参考答案:几何因素
Whenever we met, Lily greet me first though I was younger than her.[ ]
A. must
B. would
C. should
D. could
世界上最主要的、应用范围最广的固定翼航空器是()。