Answer:
the opportunity cost of producing the item relative to a trading partner's opportunity cost
Step-by-step explanation:
Comparative Advantage is a term that is used in economics to describe the position in which a country has the capacity to produce commodities or services at a cheaper opportunity cost compared to a particular country.
Hence, in this case, a nation's comparative advantage in the production of an item is determined by "the opportunity cost of producing the item relative to a trading partner's opportunity cost."