Final answer:
Option OA is the correct answer. The European Union is distinguished from the United Nations by its ability to pass laws that member states must adhere to, reflecting its significant supranational authority and influence on both domestic and collective policies of its member nations.
Step-by-step explanation:
A major difference between the United Nations and the European Union is that the European Union is able to pass laws that its member states are expected to follow. The EU possesses a significant level of supranational authority over its member nations, which includes the enforcement of economic and environmental regulations which are the strictest in the world. While the United Nations serves as a forum for countries to express and represent their own interests internationally, the EU has the ability to interfere in domestic issues, such as requiring Greece to reduce its national debt or addressing Spain's overfishing problem.
In contrast to the UN, most EU countries have adopted the common currency, the euro, and the Schengen Area allows for free movement across member countries' borders. Countries seeking EU membership must align their legislation with EU criteria, demonstrating the depth of EU's influence on domestic policies and legislation of member states. Moreover, the EU develops policy in a wide range of areas including defense, foreign affairs, immigration, and labor, which applies to each member state, emphasizing the EU's authority and cohesive attempt to forge a European identity beyond individual national identities.