单项选择题

In the piping systems of a vessel , what type of valve gives the least resistance to fluid flow when fully open?（）.

A.Globe valve
B.Butterfly valve
C.Gate valve
D.Packless valve

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单项选择题
In the presence of external forces ,the center of buoyancy of an inclined vessel is vertically aligned with the（）.

A.center of gravity
B.metacenter
C.center of flotation
D.keel
单项选择题
In writing up the log book at the end of your watch , you make an error .which of the following is the way to correct the error?（）.

A.Carefully and neatly erase the entryand rewrite it correctly
B.Remove this page of the log book and rewrite all entries on a clean page
C.Blot out the error completely and rewrite the entry correctly
D.Cross out the error with a single line and rewrite the entry correctly
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