单项选择题
The light on a life jacket must be replaced（）.
A.when the power source is replaced B.each year after installation C.every six months D.when it is no longer serviceable
单项选择题 The lifesaving equipment on all vessels shall be（）.
单项选择题 The life jackets on all vessels shall be（）.
单项选择题 The last shot of an anchor cable is usually painted（）.
