Question: who was prime minister when britain joined the common market
[{'answer': 'Edward Heath', 'provenance': [{'wikipedia_id': '615646', 'title': '1975 United Kingdom European Communities membership referendum', 'start_paragraph_id': 1, 'start_character': 571, 'end_paragraph_id': 1, 'end_character': 583, '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': 145, 'end_paragraph_id': 1, 'end_character': 734, 'bleu_score': 0.7693341411589001, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8930356418722954873}, 'section': 'Section::::Abstract.'}]}]