（）最容易在主、副切削刃的工作边界处形成。
A.氧化磨损
B.扩散磨损
C.冷焊磨损
D.磨料磨损
参考答案：A
—Have you ____ been to our town before?
—No, it’s the first time I ___ here.
A．even, come
B．even, have come
C．ever, come
D．ever, have come
横弯褶皱作用及其特点。
