單項選擇題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


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1.單項選擇題On cargo booms，preventers are（）.

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

2.單項選擇題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

3.單項選擇題Lines or gear NOT in use should be（）.

A.conspicuously marked
B.stowed anywhere
C.left on deck
D.secured or stowed out of the way

5.單項選擇題In plugging submerged holes on a vessel，rags，wedges，and other materials should be used in conjunction with plugs to（）.

A.reduce the water pressure on the hull
B.reduce the water leaking around the plugs
C.prevent progressive flooding
D.reduce the possibility of stress fractures