<image 1> The diagram above represents the idealized titration curve for the reaction of sodium oxalate ($Na_2C_2O_4$) with a strong acid like hydrochloric acid ($HCl$). E and F represent the pH at the endpoints. G and H will depend on the composition of the sample with the possibility that one may not be present. In addition to water, what are the predominant species in solution at E?
['$Na_2C_2O_4$ and $HCl$', '$Na^+$, $Cl^-$, and $HC_2O_4^-$', 'C_2O_4^{2-} and $H^+$', '$Na^+$, $H^+$, and $C_2O_4^{2-}$']