单项选择题
The signal man assisting a crane operator has his arm extended with his fingers closed and thumb pointing upward. This is the signal to（）.
A.raise the boom
B.raise the hook
C.raise the boom and hook
D.check the boom stop
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相关考题
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单项选择题
The rope which is the lightest is（）.
A.manila
B.nylon
C.polypropylene
D.dacron -
单项选择题
The rope which is rove from the truck to be used with a bos’n chair is called a（）.
A.gantline
B.life line
C.strop
D.whip -
单项选择题
The rolling hitch could be used to（）.
A.join two lines of different sizes
B.join two lines of equal sizes
C.add strength to a weak spot in a line
D.act as a stopper to transfer a line under strain
