The answer is (iv). Displacement reaction.
Reason: To create Aluminium oxide, oxygen from ferrous oxide is transferred to Aluminium metal. Aluminium is a more reactive metal than Fe in this reaction. Al will therefore remove Fe from its oxide. One of the elements displaces another in a chemical process known as a displacement reaction. More reactive metal here replaces less reactive metal. It is known as a single displacement reaction because only one displacement is taking place.