Concept:The Production Possibility Curve (PPC) illustrates the maximum possible output combinations of two commodities an economy can produce with fixed resources and technology.
Explanation:Resources are limited, so producing more of one commodity requires shifting resources away from the other commodity.
This movement along the PPC is known as a trade-off.
The trade-off measures the amount of the second commodity that must be given up to obtain an additional unit of the first commodity.
That sacrificed amount is called the opportunity cost.
Opportunity cost is defined as the value of the next best alternative foregone when a choice is made.
For example, if an economy decides to produce more consumer goods, it must reduce the production of capital goods.
The lost capital goods represent the opportunity cost of the extra consumer goods.
Thus, the trade-off between two commodities along the PPC directly demonstrates the opportunity cost principle, not merely scarcity or unattainable combinations.
Answer:D. opportunity cost principle