Which concept explains why a country might choose to produce a good in which it has a lower opportunity cost, rather than one in which it has an absolute advantage?

The concept is comparative advantage, which says a country should specialize in the good for which it has the lowest opportunity cost, even if it is not the best at producing that good. This means that the country gives up less of the other good when it shifts resources to produce the first good. By focusing on the product with the lowest relative cost, the country can trade for the other good at a cheaper price than competitors. For example, if Country A can make 10 cars or 5 computers and Country B can make 4 cars or 8 computers, A has a lower opportunity cost for cars and B for computers, so each should specialize in what they give up least. This specialization lets both countries end up with more goods than if they tried to produce everything on their own.