Given the Following K_a Values, Which Anion Is the Strongest

Multiple Choice

Given the following K_a values, which anion is the strongest base $\begin{array}{|l|l|}\hline \text { Acid } & \mathrm{K}_{3} \\\hline \mathrm{H}_{2} \mathrm{CO}_{3} & 4.2 \times 10^{-7} \\\hline \mathrm{HCO}_{3}^{-} & 4.8 \times 10^{-11} \\\hline \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} & 6.5 \times 10^{-2} \\\hline \mathrm{HC}_{2} \mathrm{O}_{4}^{-} & 6.1 \times 10^{-5} \\\hline \mathrm{H}_{2} \mathrm{PO}_{4}^{-} & 6.2 \times 10^{-8} \\\hline\end{array}$

A) HCO₃^-
B) CO₃^2-
C) HC₂O₄^-
D) C₂O₄^2-
E) HPO₄^2-