What happens to the demand curve when all non-price determinants of demand are held constant while the price changes?

When considering the impact of a price change on the demand curve while holding all non-price determinants constant, the correct observation is that the quantity demanded changes along the curve.

In microeconomics, the demand curve represents the relationship between the price of a good and the quantity demanded by consumers. When the price of the good changes, and all else remains equal (non-price determinants such as consumer preferences, income levels, and prices of related goods do not change), the movement occurs along the existing demand curve. This movement indicates a change in quantity demanded—if the price decreases, the quantity demanded typically increases, and vice versa.

This concept distinguishes between changes in demand and changes in quantity demanded. A change in demand would involve a shift of the entire curve, which occurs only when non-price determinants change. Thus, since the scenario specifies that these determinants are held constant, the shape of the demand curve remains unchanged, and any change occurs solely as a movement along the curve due to the price variation.