In the following sets of reactants which two sets best exhibit the amphoteric character of Al_2 O_3 · x H_2 O? Set 1: Al_2 O_3 · x H_2 O ( s ) and…

In the following sets of reactants which two sets best exhibit the amphoteric character of $\displaystyle \mathrm{Al}_2 \mathrm{O}_3 \cdot x \mathrm{H}_2 \mathrm{O}$ ? Set $\displaystyle 1$ : $\displaystyle \mathrm{Al}_2 \mathrm{O}_3 \cdot x \mathrm{H}_2 \mathrm{O}(\mathrm{s})$ and $\displaystyle \mathrm{OH}^{-}(\mathrm{aq})$ Set $\displaystyle 2$ : $\displaystyle \mathrm{Al}_2 \mathrm{O}_3 \cdot x \mathrm{H}_2 \mathrm{O}(\mathrm{s})$ and $\displaystyle \mathrm{H}_2 \mathrm{O}(l)$ Set $\displaystyle 3$ : $\displaystyle \mathrm{Al}_2 \mathrm{O}_3 \cdot x \mathrm{H}_2 \mathrm{O}(\mathrm{s})$ and $\displaystyle \mathrm{H}^{+}(\mathrm{aq})$ Set $\displaystyle 4$ : $\displaystyle \mathrm{Al}_2 \mathrm{O}_3 \cdot x \mathrm{H}_2 \mathrm{O}(\mathrm{s})$ and $\displaystyle \mathrm{NH}_3(\mathrm{aq})$