The pair, in which ions are isoelectronic with \( \mathrm{Al^{3+}} \) is:
\( \mathrm{Br^-} \) and \( \mathrm{Be^{2+}} \)
\( \mathrm{Cl^-} \) and \( \mathrm{Li^+} \)
\( \mathrm{S^{2-}} \) and \( \mathrm{K^+} \)
\( \mathrm{O^{2-}} \) and \( \mathrm{Mg^{2+}} \)