The correct answer is C. movement on the same demand curve.
A change in quantity demanded refers to a movement along a demand curve, which is caused by a change in the price of the good. A change in demand refers to a shift of the demand curve, which is caused by a change in any other factor that affects demand, such as income, the price of related goods, or consumer tastes.
Option A is incorrect because an upward shift of the demand curve refers to an increase in demand, which is caused by an increase in any of the factors that affect demand.
Option B is incorrect because a downward shift of the demand curve refers to a decrease in demand, which is caused by a decrease in any of the factors that affect demand.
Option D is incorrect because a change in quantity demanded is a movement along a demand curve, not a shift of the demand curve.