Chọn a.
2H2+ O2 $\buildrel{{t^o}}\over\longrightarrow$ 2H2O
2Mg+ O2 $\buildrel{{t^o}}\over\longrightarrow$ 2MgO
3Fe+ 2O2 $\buildrel{{t^o}}\over\longrightarrow$ Fe3O4
2Cu+ O2 $\buildrel{{t^o}}\over\longrightarrow$ 2CuO
S+ O2 $\buildrel{{t^o}}\over\longrightarrow$ SO2