Match the descriptions to firearm and ammunition components.
A. Metallic protrusion...: "Metallic protrusion where the primer gets compressed and explodes whilst the hammer strikes the primer". This is the Anvil, a primer component. Thus, A matches III.
B. A cardboard or a plastic disc...: "A cardboard or a plastic disc of 12mm thickness to cushion the wad". This describes the Cushion Wad, a shotgun shell component. Thus, B matches II.
C. The steel block...: "The steel block which closes the breech in firearms". This defines the Breech block, a firearm action part. Thus, C matches I.
D. A cardboard or a plastic piece...: "A cardboard or a plastic piece inside the brass head of a shotgun cartridge". This is the Base wad, inside the shell head. Thus, D matches IV.
The correct matches are A-III, B-II, C-I, D-IV.