Answer:
The correct answer is letter "A": Resource scarcity.
Explanation:
Resource scarcity is the basic economic problem by which individuals have unlimited wants and needs but rely on limited sources to fulfill them. Because of this situation, individuals have to trade-off the satisfaction of part of some needs so others can be satisfied as well.
In the example, the scarce resource is the milk that is useful to produce cheese for the pizzas sold in Wisbane.