Final answer:
The correct statement is D, which states that a change in quantity demanded is a movement along the demand curve, while a change in demand signifies a shift of the entire demand curve due to external factors.
Step-by-step explanation:
The correct statement among those provided is (D) A change in quantity demanded is a movement along the demand curve, and a change in demand is a shift of the demand curve. When there is a change in quantity demanded, it is represented by a movement along the demand curve either up or down, depending on whether the price has risen or fallen. In contrast, a change in demand signifies a shift of the entire demand curve to the left or right. This shift occurs as a response to external factors such as changes in consumer preferences, income levels, prices of substitutes or complements, or any other demand determinant.
For example, an advancement in technology for a video game might increase its demand, causing the demand curve to shift right, indicating more quantity demanded at every price level. Conversely, if the gaming system becomes outdated, the demand for the video game might decrease, resulting in a shift of the demand curve to the left.