單項(xiàng)選擇題Some cranes are mounted in pairs on a common platform which can be rotated through（）.

A.360°
B.270°
C.180°
D.90°


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1.單項(xiàng)選擇題Deck cranes require（） time to prepare for working cargo than derricks.

A.less
B.more
C.many
D.much

2.單項(xiàng)選擇題The duty of a deck winch is to lift and lower a load by means of a fixed rope on （）.

A.a warp end
B.a mooring winch
C.a worm gear
D.a barrel

3.單項(xiàng)選擇題Most anchor handling equipment incorporates （） for mooring purposes.

A.cable lifters
B.spur wheels
C.bollard
D.warpends

4.單項(xiàng)選擇題A variable displacement system of hydraulic drives consists of （）.

A.a variable displacement axial piston pump
B.a constant displacement axial piston pump
C.a reciprocating piston pump
D.a centrifugal pump

5.單項(xiàng)選擇題Which of the following hydraulic systems is not one of the three sub-division of the Hydraulic drive system?（）

A.Constant pressure system
B.Variable pressure system
C.Variable displacement system
D.Constant volume system