The correct answer is C.
The European Union is not only an economic union, with a common market and currency. It has reached an even further degree of integration by establishing some common policies related to political foreign and inner affairs. The free markets and no-borders approach applies to goods and services, but also to people.
The concept of European citizenship was created, and it was established that nationals from all EU member states could freely move from one country to another within the union without the requirements that would be required in any other countries outside: visas, permits, etc.
