Answer:
Euro
Step-by-step explanation:
The Euro became in January 1, 1999 the official currency of the 11 Memeber states (that soon increased with time).
The Euro became the international currency for the exchange and finantial operations among the members.
People used both their currency and the progressive use of Euro enabled the barrier of exchanging money, and the associated risks in European trade.
This means the first years saw macroeconomic stability, and the Central European Bank lowered inflation rates among EU members.
Lower interest rates also incentivated the Eu.
Interestingly to note: Greece was the 12th Member to adopt the currency and today it no longer has it.
Many promises the Euro made are now questioned.