单项选择题
A.a draft
B.a freeboard
C.an air draft
D.an under-keel clearance
单项选择题 Vessel must be（）duly qualified officers and crew.
单项选择题 You are in charge of a power-driven vessel navigating at night.You sight the red sidelight of another vessel on your port bow.The other vessel’s aft masthead light is to the right of her forward masthead light. You should（）.
单项选择题 You will find information about the duration of slack water in the（）.