Concept:It is a trade bloc with free trade among members and a common external tariff against non-members.
Explanation:The arrangement described has two main features.
First, member countries remove all trade barriers among themselves.
Second, they charge a common tariff against non-member countries.
A free trade area removes internal barriers but allows each member to keep its own external tariffs.
A common market also allows free movement of labour and capital.
An economic community is a broader form of integration.
Only a customs union combines a free trade area with a common external tariff.
Therefore, this description matches option C.
Answer:C. custom union