Which of the hydrated species can exist?
I. $H_5{O}_2^{+}$
II. $H_3{O}^{+}$
III. $H_3{O}_2^{-}$
IV. $H_7{O}_3^{+}$
Select alternate from.

Water on self ionization form $H_3{O}^{+}$. Water in strong acid also lead  to the formation of $H_5{O}_2^{+}$, $H_7{O}_3^{+}$ and water in strong alkali also lead to the formation of ${H_3{O}_2}^{-}$. So all the hydrated species can exist.