一个的φ300+0.050mm的孔在同一个钻床上经钻削、扩削和铰削（）加工而成。
A.三个工序
B.三个工步
C.三次进给
参考答案：B
—Are you satisfied with the answer?
—Not at all. It couldn't have been ______.
A．worse
B．so bad
C．better
D．the worst
绘图题：画出如图所示轴的剖面图和剖视图。
