Concept:A free trade area allows member countries to trade among themselves without tariffs while keeping their own separate tariffs on imports from non-members.Explanation:In a free trade area, member nations remove trade barriers such as duties on goods traded within the group.However, each member country is free to impose its own duties on goods coming from countries outside the free trade area.This is different from a customs union or common market, where members adopt a common external tariff policy.Since the question asks which integration allows a member nation to independently impose duties, the correct option is a free trade area.Answer:B. free trade area