Concept:Regional economic integration has different stages, each adding more policy coordination.
Explanation:A free trade area only removes internal tariffs among member countries.
A customs union adds a common external tariff on imports from non-members.
A common market allows free movement of labour, capital, goods, and services.
An economic union goes further by harmonising monetary and fiscal policies of member states.
Therefore, harmonised monetary and fiscal policies are a key feature of an economic union.
Answer:B. an economic union.