The trade-off between two commodities along the Production Possibility Curve (PPC) shows

1. Analyze the question The question asks what a trade-off between two commodities along the PPC illustrates.

2. Explain the concept The Production Possibility Curve (PPC) shows the maximum combinations of two goods an economy can produce when its resources are fully and efficiently used. Every point on the curve is attainable and efficient.

Because resources are limited, producing more of one good means producing less of the other. The amount of one good given up to get more of the other is the opportunity cost. This is the "trade-off."

3. Step-by-step solution

• A. Transferable output: Output is not transferred. Resources are shifted between uses, which is not the concept being tested.
• B. Unattainable combination: These are points outside the PPC, not points along it.
• C. Scarcity principle: Scarcity is the underlying reason the PPC bends or slopes downward. But the trade-off itself, giving up one good for another, is what we call opportunity cost.
• D. Opportunity cost principle: Moving from one point on the curve to another means sacrificing some units of one good for more units of the other. This is exactly opportunity cost.

Example: A farmer in Kano can use his land for maize or millet. If he moves from 10 bags of maize and 2 of millet to 8 bags of maize and 5 of millet, the opportunity cost of 3 extra bags of millet is 2 bags of maize.

4. Answer The correct option is D. opportunity cost principle.

5. Exam tip Link the PPC terms like this:

• Along the curve: trade-off and opportunity cost
• Outside the curve: unattainable
• Inside the curve: underutilization of resources or inefficiency
• Reason the PPC exists: scarcity

If you see "trade-off," "sacrifice," or "give up," think opportunity cost.