单项选择题
A.Hydraulic oil
B.Lubricating oil
C.Diesel oil
D.Refrigeration oil
单项选择题 Which of the listed fire extinguishers is recommended for use on an electrical switchboard fire?（）
单项选择题 Which of the fire extinguishing agents listed is the safest to use when combating a class C fire?（）
单项选择题 Which of the following represents the emergency signal for fire aboard ship?（）