A proper look-out shall be maintained（）.

单项选择题A proper look-out must be kept（）.

A.only in fog
B.only between the hours of sunset and sunrise
C.only when entering and leaving port
D.at all times

单项选择题A head-on situation at night is one in which you see（）.

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（）.

A.humidity
B.varying densities of water
C.vessel traffic
D.the jet stream

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.

A.besides
B.excepted
C.otherwise
D.other than

单项选择题The Rules state that vessels may depart from the Rules when（）.

A.there are other vessels in the vicinity
B.operating in a traffic separation scheme
C.engaged in a situation involving more than two vessels
D.necessary to avoid immediate danger