单项选择题
A. slacked off B. taken in C. send away D. send out
When the derrick is topped, the guys must be （）.A. slac...
单项选择题When the derrick is topped, the guys must be （）.
A. slacked off B. send away C. taken in D. send out
Do you want the derrick adjusted （）?A. up and downB. up...
单项选择题Do you want the derrick adjusted （）?
A. up and down B. upwards or downwards C. upside or downside D. forwards and backwards
The safe working load of each derrick is five （）.A.tone...
单项选择题The safe working load of each derrick is five （）.
A.tones B.tonnages C.tons D.dunnage
