单项选择题
A.aft perpendicular
B.center of buoyancy
C.keel
D.center of flotation
单项选择题 Stability is determined principally by the location of the point of application of two forces: the downward-acting gravity force and the（）.
单项选择题 Stability is determined by the relationship of the center of gravity and the（）.
单项选择题 Repair of vital machinery and services on a ship should be accomplished（）.