单项选择题
A.flashes at regular intervals of 50-70 flashes per minute B.is yellow in color C.shows an unbroken light over an arc of the horizon of not less than 180°nor more than 225° D.All of the above
A.engaged on pilotage duty B.in distress C.at anchor D.being overtaken in a narrow channel
A.a vessel meeting another head-on B.a vessel overtaking another in a narrow channel C.a vessel crossing the course of another D.the give-way vessel in a crossing situation