单项选择题
Freeboard is measured from the upper edge of the（）.
A.bulwark B.deck line C.gunwale bar D.sheer strake
单项选择题 Frapping lines（）.
单项选择题 Forty-five fathoms is marked on the anchor chain by（）.
单项选择题 Forces within a drilling unit have caused a difference between the starboard and port drafts. This difference is（）.
