Answer
c. the increase in the prices of grapes, an input into jelly
Work Step by Step
The other three choices are examples of changes that will shift the demand curve for jelly. A change in demand moves equilibrium quantity and price of a good in the same direction. For example, an increase in consumer income would shift the demand curve to the right and increase both the equilibrium quantityand price of jelly. On the other hand, the increase in the price of an input will decrease the supply of jelly, which will shift the supply curve to the left. In this case, the new equilibrium quantity for jelly will decrease and the equilibrium price will increase.
