Which are the conjugate bases of the strong acids $HClO_4$,$H_2SO_4$,$HNO_3$,and $HPO_4^{2-}$? Are they strong or weak?

(N/A) The conjugate bases are formed by removing a proton $(H^+)$ from the acid.
$1$. For $HClO_4$,the conjugate base is $ClO_4^-$.
$2$. For $H_2SO_4$,the conjugate base is $HSO_4^-$.
$3$. For $HNO_3$,the conjugate base is $NO_3^-$.
$4$. For $HPO_4^{2-}$,the conjugate base is $PO_4^{3-}$.
Since $HClO_4$,$H_2SO_4$,and $HNO_3$ are strong acids,their conjugate bases ($ClO_4^-$,$HSO_4^-$,$NO_3^-$) are very weak. $HPO_4^{2-}$ is a weak acid,so its conjugate base $PO_4^{3-}$ is relatively stronger.