给定一篇英语文章，找出所有冠词“a”或“an”的使用并将其替换为“the”。
When a new country joins the European Union, it must adopt the euro as its currency. This process is not immediate and takes some time. Before a country can adopt the euro, it must first meet certain economic criteria. An independent group of experts assesses whether a country has met these criteria, and if so, the country can begin using the euro.
When the new country joins the European Union, it must adopt the euro as the currency. This process is not immediate and takes some time. Before the country can adopt the euro, it must first meet certain economic criteria. The independent group of experts assesses whether the country has met these criteria, and if so, the country can begin using the euro.