单项选择题
When the derrick is lowered, the guys must be （）.
A. slacked off
B. taken in
C. send away
D. send out
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相关考题
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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 -
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 -
单项选择题
The safe working load of each derrick is five （）.
A.tones
B.tonnages
C.tons
D.dunnage
