Concept:An economic bloc that promotes free trade internally while applying a unified tariff policy externally.
Explanation:A customs union is a stage of economic integration where member countries remove trade barriers such as tariffs and quotas among themselves.
At the same time, all members adopt identical tariffs and trade restrictions against countries outside the union.
This is called a common external tariff.
A customs union does not necessarily include free movement of labour and capital, a shared currency, or a common military defence, which are features of deeper unions or political alliances.
Answer:B. common tariffs against non-Members.