单项选择题
A.---•(三长一短声,连放汽笛1min) B.---••(三长两短声,连放汽笛1min) C.-(警报器或汽笛一长声,连放30s)
A.人员落水 B.船上甲板失火 C.船舶机舱失火
A.七短一长声,连放汽笛1min B.三长一短声,连放汽笛1min C.两长一短声,连放汽笛1min