Technically it's not 0% either. Technically it's unsolvable. There is 0% chance you'll get a correct answer because the two 25's make 50% the "right" answer which would then make 25% the right answer and so on. And saying 0% isn't really an option because it's not one of the choices so it invalidates the question entirely.
It's called a self referential enigma and it makes my brain hurt.