Concept:Internal trade refers to the exchange of goods and services within the borders of one country.
Explanation:When buyers and sellers reside in the same country, the trade is classified as internal trade.
It is also called domestic trade because it occurs inside a nation's boundaries.
International trade and foreign trade both involve transactions between different countries, so they are incorrect here.
Barter is the direct exchange of goods without the use of money, not a general term for buying and selling within a country.
Therefore, the most accurate option is internal trade.
Answer:D. internal trade