Correct Answer: (c) Only 12 states of European Union
Solution:As per the question period, euro was the official currency of only 12 EU member countries. At present, it is the official currency of 20 out of 27 EU member countries. The 7 EU countries that do not use the euro as their official currency are Bulgaria, Czech Republic, Denmark, Hungary, Poland, Romania and Sweden. The euro currency is also used officially by the institutions of the EU, by four European microstates (Andorra, Monaco, San Marino and Vatican City) that are not EU members, as well as unilaterally by Montenegro and Kosovo.