单项选择题
A.a positive righting moment
B.an increase in KM
C.a negative restoring force
D.a positive restoring force
单项选择题 In a river subject to tidal currents，the best time to dock a ship without the assistance of tugs is（）.
单项选择题 If your vessel is dragging her anchor in a strong wind，you should（）.
单项选择题 If you were being assisted by an icebreaker and he sent you the single letter Q，he would be telling you（）.