单项选择题
A ship is inclined at an angle of loll. In the absence of external forces，the righting arm (GZ) is（）.
A.positive B.negative C.zero D.vertical
单项选择题 A partially full tank causes a virtual rise in the height of the（）.
单项选择题 A neutral equilibrium position for a vessel means that the metacenter is（）.
单项选择题 A load line of a ship is assigned by（）.
