Classify the following reactions into different types, giving reason.
(a) It is a Combination reaction because two substances combine to form single product.
(b) It is a neutralization reaction because a base (potassium hydroxide) reacts with an acid (hydrochloric acid) to form salt (potassium chloride) and water.
(c) It is a displacement reaction because copper displaces silver from silver nitrate solution to form copper nitrate solution.
(d) It is a decomposition reaction because barium carbonate decomposes to form barium oxide and carbon dioxide.