When an Economist Says That the Demand for a Product

When an economist says that the demand for a product has increased,he or she means that:

A) consumers are now willing to purchase more of this product at every price
B) the product has become particularly scarce for some reason
C) the product's price has fallen and, consequently, consumers are buying a larger quantity of the product
D) the demand curve has shifted to the left
E) the product has suddenly become plentiful