Final answer:
d. Change in quantity demanded
A change in demand refers to a shift of the demand curve where consumers buy different quantities at every price; this is distinct from a movement along a demand curve, which is caused by a price change.
Factors like income increase can cause demand to shift, affecting the equilibrium price and quantity without shifting the supply curve. The new equilibrium is found by the movement along the supply curve.
Step-by-step explanation:
A change in demand refers to a situation where, for various reasons, consumers change the quantity they are willing to buy at every price point, resulting in a shift of the entire demand curve.
This should not be confused with a movement along a given demand curve, which happens when there is a change in the quantity demanded due to a change in price.
A shift in demand could occur for several reasons, such as an increase in income, changes in tastes and preferences, the price of related goods, expectations about the future, and the number of buyers.
When there is a shift in demand, the new equilibrium quantity and price in the market will change accordingly.
For example, if consumers experience an income increase, they may decide that they can afford to buy more of a good at any given price, resulting in the demand curve shifting to the right.
It is important to understand that a shift in one curve (demand in this case) never causes a shift in the supply curve. Instead, it causes a movement along the supply curve to reach a new equilibrium.