YS14切丝机刀辊体开启角度是()。
A.30°
B.40°
C.50°
D.60°
参考答案:B
He was so helpful that we ____ him as direct.[ ]
A. chose
B. found
C. elected
D. put
实施井下作业时,常用的动力提升设备是()。
A、作业架
B、通井机
C、吊卡
D、以上都不是