轧机的利用系数是指理论上可能的轧制节奏时间与实际的轧制节奏时间的比值，即T理/T实。
参考答案：对
— Why don't you like your job?
— It's always being ______ by mydirector. [ ]
A. watched at
B. watched out
C. watched over
D. watched on
车削矩形螺纹的刀具主要有：45°车刀、90°车刀、（）刀、矩形螺纹车刀、内孔车刀、麻花钻、中心钻等。
A.铣
B.切槽
C.圆弧
D.锉
