The acidity of diprotic acid in aqueous solutions increases in the order.

Consider the following reactions.

I. ${\mathrm{AlH}}_3+{\mathrm{H}}^{-}\to {{\mathrm{AlH}}_4}^{-}$

II. ${\mathrm{H}}_2\mathrm{O} + {\mathrm{H}}^{-}\to {\mathrm{H}}_2 + {\mathrm{OH}}^{-}$

Select the correct statements from the following.