Question: when did the uk become part of eu
[{'answer': 'on 1 January 1973', 'provenance': [{'wikipedia_id': '615646', 'title': '1975 United Kingdom European Communities membership referendum', 'start_paragraph_id': 1, 'start_character': 516, 'end_paragraph_id': 1, 'end_character': 533, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '615646', 'title': '1975 United Kingdom European Communities membership referendum', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 734, 'bleu_score': 0.874447736097245, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13988917997462640284}, 'section': 'Section::::Abstract.'}]}]