Final answer:
The statement is true. When moving along a demand curve, the only factor that changes is buyers' income.
Step-by-step explanation:
The statement is true. When moving along a demand curve, the only factor that changes is buyers' income. All other factors such as price, taste, and availability of substitutes remain constant. As buyers' income increases, their purchasing power increases, which leads to an increase in demand for normal goods. On a graph, this is shown by a shift of the demand curve to the right.