Which of the following is an example of combination reaction?
1
2Mg (s) + O2 (g) → 2MgO (s)
2
Fe2O3 (s) + 2Al (s) → Al2O3 (s) + 2F3 (s)
3
CaCO3 (s) → CaO (s) + CO2 (g)
4
Fe (s) + CuSO4 (aq) → FeSO4 (aq) + Cu (s)
Which of the following is an example of combination reaction?