What is LEAST likely to cause ignition of fuel vapors?（）.

A.Stores such as line，rags，mattresses，linens，etc. must be treated to be fire retardant
B.Stores certified for use on uninspected vessels may be identified by the certification number used by Underwriter's Laboratories
C.A portable container of a flammable liquid used as fuel for portable auxiliary equipment must be stowed in a paint locker or at a designated open location
D.Acetylene may be in a ship's storeroom in quantities not exceeding 6000 cubic feet

A.Up to five gallons of a flammable liquid may be stowed in the engine room
B.All stores of line，rags，linens and other similar type stores must be certified by UL as being fire retardant
C.Cylinders containing compressed gasses must be constructed and tested in accordance with the Bureau of Standards
D.All distress flares when received must be stored in the portable magazine chest