单项选择题
The center of volume of the immersed portion of the hull is called the（）.
A.center of buoyancy B.center of floatation C.center of gravity D.tipping center
单项选择题 The collision bulkhead shall be of（）.
单项选择题 The deck control valve to be（）after being repaired.
单项选择题 The disinfection of various compartment in a vesel by filling them with a gaseous agents to destroy rats ect.means（）.
