Suppose that both the equilibrium price and quantity of ketchup fall. The most consistent explanation for these observations is:
A.a decrease in demand for ketchup with no change in supply.
B.an increase in demand for ketchup with no change in supply.
C.an increase in the supply of ketchup with no change in demand.
D.an increase in demand for ketchup and a decrease in the supply of ketchup.
正确答案:a decrease in demand for ketchup with no change in supply.