Chapter 13, Problem 134QP

Which of the following weak acids has the anion that is the strongest base?

$\begin{array}{l}{\text{CH}}_3{\text{CO}}_2\text{H }{K}_{\text{a}} =1.8\times {10}^{-5}\\ \text{HF }{K}_{\text{a}} =6.3\times {10}^{-4}\\ {\text{HCO}}_2\text{H }{K}_{\text{a}} =1.8\times {10}^{-4}\\ \text{HCN }{K}_{\text{a}} =6.2\times {10}^{-10}\\ \text{HOCl }{K}_{\text{a}}=4.0\times {10}^{-8}\end{array}$