Which of the following is an example of a movement along the demand curve?

• A. A fall in price causes an increase in quantity demanded.
• B. An increase in income shifts demand to the right.
• C. A change in tastes shifts demand.
• D. Prices of related goods change.

Answer: (A)

Movement along the demand curve happens when the price of the good changes, causing the quantity demanded to change along the same curve while all other determinants stay the same. A fall in price lowers the price on the vertical axis and leads to a higher quantity demanded at a point lower on the curve, which is exactly a movement along the curve. The other scenarios involve non-price factors such as income, tastes, and the prices of related goods, which shift the entire demand curve rather than move along it.