单项选择题
A CO2 extinguisher on a ship which has lost 10% of its charge must be（）.
A.used at the earliest opportunity B.hydrotested C.recharged D.weighed again in one month
单项选择题 A branch line valve of a fire extinguishing system on a ship must be marked with the（）.
单项选择题 （），as the chemical extinguisher agent，should be used for an electric fire.
单项选择题 The danger of a charged hose left unattended on deck with the nozzle open is（）.
