91. Stability is determined principally by the relationship of the center of gravity and the __________.

Stability depends on the relationship between the center of gravity and the center of buoyancy, as these points create the righting lever when a vessel heels. The center of gravity represents the vessel's weight, while the center of buoyancy represents the buoyant force. The distance between these points determines the vessel's ability to return to an upright position after being heeled.