C-06-Q148mediumsingle_mcqWith 4 Mg atoms and 4 O2\mathrm{O_2}O2 molecules in 2Mg+O2→2MgO\mathrm{2Mg + O_2 \to 2MgO}2Mg+O2→2MgO, the limiting reactant is—aO2\mathrm{O_2}O2bMgcbothdneither