单项选择题
The velocity of the current in large coastal harbors is（）.
A.predicted in Tidal Current Tables B.unpredictable C.generally constant D.generally too weak to be of concern
单项选择题 The velocity of a rotary tidal current will be decreased when the Moon is（）.
单项选择题 The type of current which will have the greatest effect on the course made good for your vessel is（）.
单项选择题 The two most effective generating forces of surface ocean currents are（）.
