单项选择题
If a vessel takes a sudden severe list or trim from an unknown cause，you should FIRST（）.
A.determine the cause before taking countermeasures B.assume the shift is due to off-center loading C.counterflood on the side opposite the list or trim D.assume the cause is environmental forces
单项选择题 The disinfection of various compartments in a vessel by filling them with a gaseous agents to destroy rats etc.means（）.
