An exothermic reaction is represented by the graph:

Following species are classified into acid, base and amphiprotic species on the basis of protonic concept
($\mathrm{i}$) ${\mathrm{H}}_2{\mathrm{PO}}_2^{-}$
($\mathrm{ii}$) ${\mathrm{H}}_2{\mathrm{PO}}_3^{-}$
($\mathrm{iii}$) ${\mathrm{H}}_2{\mathrm{PO}}_4^{-}$
($\mathrm{iv}$) ${\mathrm{HPO}}_3^{2-}$
($\mathrm{v}$) ${\mathrm{HPO}}_4^{2-}$
($\mathrm{vi}$) ${\mathrm{NH}}_4^{+}$
($\mathrm{vii}$) ${\mathrm{CH}}_3{{\mathrm{COOH}}_2}^{+}$
which is correct match: