Final answer:
Authorized wear on the ribbon bar of the Navy Expert Rifleman and Expert Pistol Shot Medals is a small gold "E", representing high-level marksmanship, and if qualified in both rifle and pistol, a silver "E" is also worn for the other weapon.
Step-by-step explanation:
The decoration that is authorized for wear on the ribbon bar of the Navy Expert Rifleman and Expert Pistol Shot Medals is A) A small gold "E". This signifies the highest level of marksmanship in the Navy. If a service member qualifies as an expert with both the rifle and the pistol, they wear a gold "E" on the ribbon of the weapon they qualified for last and a silver "E" on the ribbon of the other weapon.