单项选择题
A.two rockets，one of which shall be the buoyant type
B.three rockets，one of which shall be the buoyant type
C.four rockets，two of which shall be the buoyant type
D.five rockets，two of which shall be the buoyant type
单项选择题 In order for the automatic lifeboat drain to operate properly（）.
单项选择题 In launching a covered lifeboat，what would safely lower the lifeboat from inside the lifeboat cabin?（）
单项选择题 In addition to the life jackets stowed at each berth location，life jackets must be stowed at each watch station and（）.