To determine which metal can be used to reduce alumina ($$Al$_2$O$_3$), we need to refer to the Ellingham diagram.$\\$The Ellingham diagram is a graph that shows the temperature dependence of the stability of compounds.$\\$It plots the standard free energy change ($\Delta G^\circ$) of formation of oxides versus temperature.$\\$In the Ellingham diagram, a metal can reduce the oxide of another metal if its line is below the line of the other metal's oxide.$\\$This is because the metal with the lower $\Delta G^\circ$ value for its oxide formation is more stable,$\\$and thus can reduce the oxide of the metal with the higher $\Delta G^\circ$ value.$\\$Let's analyze the options:$\\$• $$Mg: Magnesium's line is below that of alumina, indicating it can reduce alumina.$\\$• $$Zn: Zinc's line is above that of alumina, so it cannot reduce alumina.$\\$• $$Fe: Iron's line is also above that of alumina, so it cannot reduce alumina.$\\$• $$Cu: Copper's line is above that of alumina, so it cannot reduce alumina.$\\$Therefore, magnesium (Mg) is the only metal among the given options that can be used to reduce alumina.$\\$This corresponds to Option 1.