(D) (ii) and (iii)
In reaction (ii) MgO + H₂O → Mg(OH)₂ and (iii) 4Al + 3O₂ → 2Al₂O₃, two reactants combine to form a single product — these are combination reactions.
A combination reaction is one where two or more substances combine to form a single product. Reaction (i) is decomposition (one reactant → multiple products) and reaction (iv) is a displacement reaction. Examiners expect students to correctly identify the defining feature: single product from multiple reactants.