A nation's comparative advantage is determined by

A) the total cost of production.
B) the quantity of resources required to produce a unit of output.
C) the opportunity cost of producing an item relative to a trading partner's opportunity cost of producing the same item.
D) specialization in the production of all goods.

Comparative advantage is determined by the opportunity cost of producing an item relative to a trading partner's opportunity cost of producing the same item. This means that a nation will specialize in producing the goods that have relatively lower opportunity costs compared to their trading partner, and trade these goods for the ones that have relatively higher opportunity costs.