${\mathrm{K}}_{\mathrm{a}}$ values for acids ${\mathrm{H}}_2{\mathrm{SO}}_3,{\mathrm{HNO}}_2,{\mathrm{CH}}_3\mathrm{COOH}$ and $\mathrm{HCN}$ are respectively $1.3\times {10}^{-2},4\times {10}^{-4}, 1.8\times {10}^{-5}$  and $4\times {10}^{-10},$ which of the above acids produces stronger conjugate base in aqueous solution?