Answer:
common market
Explanation:
We are not told anything about the political status of contries A, B and C, so we should assume that they lack political unity, therefore they are forming only a common market.
A common market is defined by a group of countries that impose few or no duties to common trade between them, but impose common tariffs on external trade.
The European Union started as a common market during the 1960s and 1970s known as the European Economic Community. Then it evolved into a political union. Another example would be the Mercosur in South America.
