While conducting a lawful pat search, an officer found a handgun in the person's coat pocket. On inspection, the officer noticed that the handgun was unloaded and that the suspect had a license to carry the weapon. The officer also noticed that all identification marks had been obliterated by file marks. The suspect stated he purchased the firearm and was unaware of the altered identification marks. What crime, if any, has occurred?
a) Possession of a firearm with altered identification marks
b) Illegal carrying of an unloaded firearm
c) Unlawful possession of a firearm
d) No crime; the suspect has a valid license to carry the weapon.