单项选择题
A.Leaves a residue
B.Cost，relative to other agents
C.Breaks down while under prolonged storage
D.Conducts electricity
单项选择题 Which characteristic is an advantage of Halon as a fire extinguishing medium?（）
单项选择题 Which action is routinely performed at the annual servicing and inspection of a dry-chemical cartridge-operated portable fire extinguisher?（）
单项选择题 Where would you find the FCC authorization for transmitting on your ship’s EPIRB?（）