单项选择题
According to the regulations，what fire safety control feature is required in quick-closing shut off valves?（）
A.Electrical cut off switch B.A fusible link C.Manual cut off switch D.A water spray actuator
单项选择题 A vessel is constructed with a steel hull and an aluminum superstructure. Which statement is TRUE?（）
单项选择题 A squeeze-grip type carbon dioxide portable fire extinguisher has been partially discharged. It should be（）.
单项选择题 A spring line is（）.
