单项选择题
A current perpendicular to a vessel’s track has the greatest effect on the vessel’s course made good（）.
A.at high vessel speeds B.at low vessel speeds C.in shallow water D.in deep water
单项选择题 A condition where two currents meet at the downstream end of a middle bar can be determined by a（）.
单项选择题 A coastal current（）.
单项选择题 A backlash below a lock is defined as（）.
