单项选择题
The helm command PORT TWENTY means（）.
A.change course twenty degrees to the left B.put the rudder left twenty degrees C.put the rudder hard left for the first twenty degrees of swing D.put the rudder left twenty degrees and then ease back as the vessel starts swinging
单项选择题 The circulation around a low pressure center in the Northern Hemisphere is（）.
单项选择题 How long are you prohibited to consume alcohol prior to serving as a member of a watch?（）
单项选择题 It is dangerous for vessels without the operational radar（）the estuary.
