单项选择题
A. gooseneck B. guy C. center guy D. stay
The（）(贵重货) must be kept carefully.A.VCB.PCC.A+BD.NC
单项选择题The（）(贵重货) must be kept carefully.
A.VC B.PC C.A+B D.NC
The （）(支索)is important to a derrick.A. blockB. guyC. st...
单项选择题The （）(支索)is important to a derrick.
A. block B. guy C. stay
The （）(吊杆托架) supports the derrick.A. derrick boom restB...
单项选择题The （）(吊杆托架) supports the derrick.
A. derrick boom rest B. derrick head C. derrick mast D. derrick guy
