单项选择题
A.two balls in a vertical line
B.two diamonds in a vertical line
C.a single black ball
D.no shape is shown during the day
单项选择题 During the course of a voyage，a seaman falls on the main deck and injures his ankle. The Master should submit a Report of Marine Accident，Injury or Death if the（）.
单项选择题 During storm conditions on a ship，the mooring tensions should be adjusted so that（）.
单项选择题 During oil transfer operations，who is responsible for ensuring that the posted transfer procedures are followed?（）