Stem: G+O = 80%, Others = 20%, O = ?
I gives G = (O+B) + 530. Insuff
II gives O= 75%(G+B). Insuff
Together, we can get
G-B = O+530
G+B = 4O/3
2G=7O/3 + 530
Doesn'e lead us anywhere, unless we know the total number of people.
I agree with this, I think it is E. We need the total number of votes. Also if we were told that there were only three candidates (G, O and B) and no abstentions: G+O+B=Total votes, then the answer would be C, but from the information given we need to suppose that there could be more candidates.