X62W铣床切削过程中，主轴产生让刀现象的可能原因是（）。
A.中轴承上锁紧螺母松动
B.主轴磨损
C.切削力过大
D.主轴刚度不够
参考答案：A
Heroes ______ their life ______ becoming the best they can be, whether it is President of the United States, a mother, or a firefighter.
A．prevent…from
B．devote…to
C．prefer…to
D．suffer…from
潜在失效及后果分析
