A.liftB.riseC.elevateD.hoistOur jumbo boom can（）20 tons……

单项选择题On which type davit does the davit head stay at the same height?（）

A.Radial
B.Sheath-screw
C.Quadrantal
D.Gravity

单项选择题On what type of pump would you find an impeller?（）

A.Centrifugal
B.Gear
C.Piston
D.Vane

单项选择题On navigational aids，what does the light characteristic Fl(2+1) mean?（）

A.A flashing light combined with a fixed light of greater brightness
B.Light flashes combined in groups，with a different number of flashes in each group
C.A light showing groups of two or more flashes at regular intervals
D.A fixed light varied at regular intervals by groups of two or more flashes of greater brightness

单项选择题On cargo booms，preventers are（）.

A.auxiliary guys
B.extra fair leads
C.steel bands
D.stops

单项选择题Mechanical gearing of deck machinery such as the windlass or boat hoists should（）.

A.be open to view so，if a foreign object gets in the gearing，the operator can immediately stop the machinery
B.have a guard over the gearing
C.be painted a contrasting color from the base color in order to call attention to the gearing
D.not be operated if there is any crew within 10 feet of the machinery