Final answer:
A movement along a demand curve due to a change in the price of the good is called a change in quantity demanded. A shift in the demand curve, which can be either to the right or left, represents a change in demand due to various external factors. The correct answer is option: a) change in quantity demanded.
Step-by-step explanation:
A movement along a demand curve from one price-quantity combination to another is called a change in quantity demanded. This occurs when the price of a good changes, leading to a movement up or down the demand curve to a new quantity demanded, without the demand curve itself shifting. The curve does not shift—it only represents the quantity demanded at each price point.
Conversely, a shift in the demand curve signifies a change in demand, which occurs due to various demand determinants such as consumer preferences, income levels, prices of related goods, and future expectations. This causes the entire curve to move to the right (increase in demand) or left (decrease in demand), leading to a new equilibrium price and quantity when intersecting with the supply curve.
In contrast, a change in supply would also result in a shift of the supply curve rather than a movement along it, which affects equilibrium outcomes in different ways compared to movements along the demand curve.