400
When the economist says that the demand for a product has increased, he/she means that:
a. the demand curve has shifted to the left
b. product price has fallen and as a consequence consumers are buying a larger quantity of the product
c. the product has become particularly scarce for some reason
d. consumers are now willing to purchase more of this product at each possible price
d. consumers are now willing to purchase more of this product at each possible price