The Figure Given Below Represents the PPC in Two Nations

The figure given below represents the PPC in two nations - Germany and Korea, producing only two goods, cars and food.Figure 2.4

-The downward slope of the demand curve is attributed to:

A) the inverse relationship between price and quantity demanded.
B) the direct relationship between income and quantity demanded.
C) the direct relationship between price and quantity demanded.
D) the inverse relationship between income and quantity demanded.
E) the direct relationship between consumer preferences and quantity demanded.