As of 2016, 18 Members of the European Union Had

As of 2016, 18 members of the European Union had adopted further economic integration than the other members by

A) abolishing tariff and nontariff barriers to trade among each other.
B) adopting uniform policies on the movement of factors of production.
C) establishing common trade policies against countries that were not members of the EU.
D) implementing a common currency and a common monetary policy.