单项选择题
A.one sidelight of a vessel ahead of you
B.one sidelight and a masthead light of a vessel ahead of you
C.one sidelight，a masthead light，and a range light of a vessel ahead of you
D.both sidelights of a vessel dead ahead of you
单项选择题 One of the factors which affects the circulation of ocean currents is（）.
单项选择题 Vessels，（）support vessels，should not enter the safety zone of a deepwater port unless clearance has been obtained from the Vessel Traffic Supervisor.
单项选择题 The Rules state that vessels may depart from the Rules when（）.