Which of the following is an example of comparative advantage in trade that involves U.S. imports and exports of non-manufactured goods with one other country? Because a lot of trade in manufactured goods is intra-industry (for example, the United States exports and imports commercial jet liners with Europe), DO NOT use manufactured goods in your answer. Also, not all the answers are factually true, just focus on the question of whether it would be an example of comparative advantage.
Group of answer choices:
1. U.S. exports Boeing planes to Europe and imports Airbus planes from Europe.
2. US exports gasoline to Mexico and imports oil from Mexico.
3. US exports military equipment to China and imports steel from China.
4. US exports sorghum (a grain) to Madagascar and imports coffee from Madagascar.