What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the following species: $HNO_2, CN^{-}, HClO_4, F^{-}, OH^{-}, CO_3^{2-}$ and $S^{2-}$

(N/A) Definition: $A$ conjugate acid-base pair is a pair of chemical species that differ by only one proton $(H^+)$. When an acid loses a proton,it forms its conjugate base,and when a base gains a proton,it forms its conjugate acid.
For the given species:
$1$. $HNO_2$: Conjugate base is $NO_2^-$.
$2$. $CN^{-}$: Conjugate acid is $HCN$.
$3$. $HClO_4$: Conjugate base is $ClO_4^-$.
$4$. $F^{-}$: Conjugate acid is $HF$.
$5$. $OH^{-}$: Conjugate acid is $H_2O$.
$6$. $CO_3^{2-}$: Conjugate acid is $HCO_3^-$.
$7$. $S^{2-}$: Conjugate acid is $HS^{-}$.