A) 2Fe3+, 6C4+, 12O2-

B) 3Fe4+, 2CO43- ; 2OH-

C) 3Fe2+, 3C2O42-

D) 3Fe4+, 2CO43- ; 2H2O2-

E) 2Fe3+, 3CO22- ; 2 H2O

I personally thought the answer would be 2 Fe(3+) and 3 C2O4(2-), but as that is not an option I'm stumped. Any insight would be great.