Answer: Option (a) is the correct answer.
Explanation:
According to Bronsted and Lowry, acid are the species which donate proton and bases are the species which accept a proton.
Therefore, [tex]H_{2}PO^{-}_{4} \rightarrow H^{+} + HPO^{2-}_{4}[/tex]
Here we can see that [tex]H_{2}PO^{-}_{4}[/tex] is an acid and [tex]HPO^{2-}_{4}[/tex] is its conjugate base.
Thus, we can conclude that the compound [tex]H_{2}PO^{-}_{4}[/tex] and [tex]HPO^{2-}_{4}[/tex] is a conjugate acid-base pair.
