Given the Following K_a Values, Which Anion Is the Strongest

Given the following K_a values, which anion is the strongest base $\begin{array}{|l|l|}\hline \text { Acid } & \mathrm{K}_{\mathrm{a}} \\\hline \mathrm{HF} & 7.1 \times 10^{-4} \\\hline \mathrm{HCOOH} & 1.7 \times 10^{-4} \\\hline \mathrm{HCN} & 4.9 \times 10^{-10} \\\hline \mathrm{HNO}_{2} & 4.5 \times 10^{-4} \\\hline \mathrm{CH}_{3} \mathrm{COOH} & 1.8 \times 10^{-5} \\\hline\end{array}$

A) F^-
B) HCOO^-
C) CN^-
D) NO₂^-
E) CH₃COO^-