No outlet on a fire hydrant may point above the horizontal in order to（）.

A.Spare charges shall be carried for at least 50 percent of each size and variety required on board
B.If the unit cannot be charged by the vessel's personnel，one spare unit shall be carried in lieu of spare charges
C.Spare charges shall be stowed in watertight containers on deck
D.Regulations concerning spare charges do not apply to unmanned barges

A.posted with instructions on the operation of the system
B.ventilated and equipped with explosion-proof switches
C.painted with red and black diagonal stripes
D.equipped with a battery powered source of emergency lighting