The correct answer is letter "B": magnitude of the response in quantity demanded to a change in price.
Explanation:
Price elasticity of demand is the measure of how quantity demanded for a good or service changes as a result of changes in price. <em>Price elasticity of demand is calculated by dividing the percentage change in quantity demanded by the percentage change in price</em>. If the result is equal or greater than one (1) the good or service is elastic. If the result is lower than one (1), the product is inelastic.
