單項選擇題

Foam-type portable fire extinguishers are more usefull in combating fires involving（）.

A.solid materials such as wood or bales of fiber
B.inflammable liquids
C.electrical equipment
D.metallic solids

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For a floating vessel, the center of buoyancy and the metacenter are in the line of action of the buoyant force（）.

A.only when there is positive stability
B.only when there is negative stability
C.only when there is neutral stability
D.at all times

單項選擇題

For a floating vessel,the center of the floating is the point in the waterpiane.（）.

A.aboat which the vessel lists and trims
B.which coincides with the center of buoyancy
C.which, in the absence of external forces, is always vertically aligned with the center of gravity
D.which is shown in the hydrostatic tables as VCB