Question: when did the last country join the eu
[{'answer': 'July 2013', 'provenance': [{'wikipedia_id': '324164', 'title': 'Enlargement of the European Union', 'start_paragraph_id': 2, 'start_character': 269, 'end_paragraph_id': 2, 'end_character': 278, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '324164', 'title': 'Enlargement of the European Union', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 529, 'bleu_score': 0.978138775770484, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12321503681851965906}, 'section': 'Section::::Abstract.'}]}]