Which of the two: $O_2NCH_2CH_2O^{-}$ or $CH_3CH_2O^{-}$ is expected to be more stable and why?

(A) $NO_2$ group is an electron-withdrawing group. Hence,it shows $-I$ effect.
By withdrawing the electrons toward it,the $NO_2$ group decreases the negative charge on the compound,thereby stabilising it.
On the other hand,the ethyl group $(CH_3CH_2-)$ is an electron-releasing group. Hence,the ethyl group shows $+I$ effect.
This increases the negative charge on the compound,thereby destabilising it.
Hence,$O_2NCH_2CH_2O^{-}$ is expected to be more stable than $CH_3CH_2O^{-}$.