Final answer:
The correct answer is D: lowest; comparative. A nation should specialize in producing and trading goods where it has the lowest opportunity cost or comparative advantage.
Step-by-step explanation:
Economizing requires that any particular good be produced by the nation having the lowest domestic opportunity cost, or the comparative advantage for that good. The correct answer is D. lowest; comparative.
In international trade, a nation has a comparative advantage in producing a product when it can do so at a lower opportunity cost compared to other nations. Conversely, a nation has an absolute advantage if it can produce the product using fewer resources than another nation. Specializing in goods where a nation has a comparative advantage, and trading for other goods, increases the global production and consumption efficiently.