Why do countries trade with each other?

Answer: To focus on what each does best and swap the rest

To move goods long distances — Wrong. Moving goods long distance is a cost of trade, not the reason for it. Countries trade because specialization makes production more efficient overall.

To focus on what each does best and swap the rest ✓ — Correct! Each country focuses on what it does best, then trades with others. Japan makes cars efficiently, Brazil grows coffee well, Saudi Arabia has oil. By specializing and trading, everyone gets more goods at lower cost than making everything alone. Economists call this comparative advantage.

To make diplomatic friends — Wrong. While trade can improve relations, that's not the economic reason. Countries trade because it's more efficient than making everything themselves.