单项选择题
A.metacentric height is positive
B.metacentric radius is positive
C.KG exceed maximum allowable limits
D.Free surfaces are excessive
单项选择题 Emergency escape breathing device on board shall have a duration of service no less than（）.
单项选择题 All engines in lifeboats and rescue boats shall be run for a total period of not less than（）in weekly inspections.
单项选择题 The master shall ensure that any seafarers（）are provided with an adequate period of rest.