And some of them aren't the former owner, they're the first owner.
So you could put Cadmus, though I agree that Marvolo ist the first one who comes to mind, so it is utterly okay tha way it is.
Marvolo Riddle however, as jmaddog waned to put it, is utterly wrong.
Thank you for a nice guiz!
Who owned Riddle's diary, possession is ownership, with the exception of Malfoy who was a caretaker for Voldemort (owner) then both Ginny and Harry owned the diary when they possessed it.
Amazing quiz btw cx
A) we don't know Cadmus even owned the ring, it could've been owned by anyone of his descendants. All we know is that Cadmus owned the stone.
B) In the book, Voldemort took the ring off his uncle Morfin, who was given it by Marvolo. Everything in-between Marvolo and Cadmus is nonexistent. So Marvolo is the original owner IN THE BOOK