单项选择题
A.wearing a life jacket
B.wearing a safety harness secured to the stage
C.wearing both a life jacket and a safety harness secured to the stage
D.the vessel is not making way
单项选择题 A vessel is to make a voyage between New York and San Juan，Puerto Rico，and return. The crew should be signed on（）.
单项选择题 A vessel is overtaking when she can see which light(s) of a vessel ahead?（）
单项选择题 A vessel is inclined at an angle of loll. In the absence of external forces，the righting arm (GZ) is（）.