WAEC Economics 2020 Paper

Concept:A shift in the demand curve from $D_{1}D_{1}$ to $D_{2}D_{2}$ represents an increase in demand for Commodity X.Explanation:An increase in demand means that consumers are willing to buy more of Commodity X at each price.When the price of a substitute good rises, Commodity X becomes relatively cheaper.As a result, consumers switch from the substitute to Commodity X, causing its demand to rise.A fall in consumer income would decrease the demand for a normal good, not increase it.A rise in the price of a complement would make the combined cost higher, so demand for X would fall.A fall in the supply of Commodity X affects the supply curve, not the demand curve.Answer:B. Rise in the price of a substitute