操作者必须熟悉车床使用说明书和车床的（）性能、结构，严禁超性能使用。
A.一般
B.整体
C.工艺
D.切削
参考答案：A
If you often feel tired and can't focus your attention, that is________you have to stop working too
hard and to have a rest.[ ]
A. why
B. whether
C. when
D. what
治理国家的两种方法分别是什么？
