Figure 4-3 -Refer to Figure 4-3.If the Demand Curve Shifts from D

Figure 4-3
-Refer to Figure 4-3.If the demand curve shifts from D to D',then

A) firms would be willing to supply less of the good than before at each possible price.
B) people are willing to buy less of the good than before at each possible price.
C) people's incomes evidently have decreased.
D) the price of the product has increased,causing consumers to buy less of the product.