The correct answer is: C. change in price
Extension and contraction of demand are the result of a change in the price of a good or service. When the price of a good or service decreases, consumers will demand more of it. This is because the good or service is now more affordable, and consumers have more purchasing power. When the price of a good or service increases, consumers will demand less of it. This is because the good or service is now less affordable, and consumers have less purchasing power.
Option A is incorrect because a change in consumer’s income will not necessarily lead to an extension or contraction of demand. For example, if a consumer’s income increases, they may choose to buy more of a good or service, but they may also choose to buy less of it. It depends on their preferences.
Option B is incorrect because a change in consumer’s tastes will not necessarily lead to an extension or contraction of demand. For example, if a consumer’s tastes change and they start to prefer a good or service more, they may choose to buy more of it. However, they may also choose to buy less of it, if they are now less interested in the good or service.
Option D is incorrect because a change in price is the only factor that will always lead to an extension or contraction of demand.