How long must the records of tests and inspections of fire fighting equipment on board a ship be retained on board?（）

A.fire fighting plan
B.shipping articles
C.Certificate of Inspection
D.muster list

A.lack of toxicity
B.the multipurpose extinguishing ability
C.burn-back protection
D.cooling ability

A.put back in service if more than 50% of the charge remains
B.repainted
C.discarded
D.recharged