Concept:International trade occurs because countries benefit from specializing in goods they can produce at a lower relative cost.
Explanation:The main reason for international trade is comparative cost advantage.
It means a country can produce a good at a lower opportunity cost than another country.
So, instead of producing everything domestically, a country imports goods that are expensive for it to make and exports goods that it can make more cheaply.
This makes trade beneficial for all participating countries.
Absolute cost advantage is not the only reason, because trade still happens even when one country is more efficient in every product.
Thus, the idea that best explains why nations trade is comparative cost advantage.
Answer:B. Comparative cost advantage