Which one of the following is a combustion reaction?
A. CH4 + 2O2 → CO2 + 2H2O
B. Ba(OH)2 + 2HClO4 → Ba(ClO4)2 + 2H2O
C. 4Fe + 4O2 → 2Fe2O3
D. Zn + HCl → ZnCl2 + H2