Which one of the following pairs of countries joined the European Union in January, 2007?

Bulgaria and Romania formally acceded to the European Union on 1 January 2007, completing the next wave of EU enlargement after the large 2004 expansion. The textbook chronology explicitly records “2007 January: Bulgaria and Romania join the EU,” confirming both countries’ accession in that month [1]. Official EU/ECB documentation likewise states that on 1 January 2007 the Union was enlarged through the accession of Bulgaria and Romania and notes their integration into EU institutions such as the European System of Central Banks [2]. Therefore the correct pair that joined in January 2007 is Bulgaria and Romania.

Sources

1. [1] Contemporary World Politics, Textbook in political science for Class XII (NCERT 2025 ed.) > Chapter 2: Contemporary Centres of Power > TIMELINE OF EUROPEAN INTEGRATION > p. 18
2. [2] https://www.ecb.europa.eu/press/pr/date/2007/html/pr070102_1.en.html