Question: who was the head of the soviet union when it collapsed
[{'answer': 'Mikhail Gorbachev', 'provenance': [{'wikipedia_id': '40494892', 'title': 'Dissolution of the Soviet Union', 'start_paragraph_id': 1, 'start_character': 761, 'end_paragraph_id': 1, 'end_character': 778, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '40494892', 'title': 'Dissolution of the Soviet Union', 'start_paragraph_id': 1, 'start_character': 335, 'end_paragraph_id': 1, 'end_character': 1128, 'bleu_score': 0.787767379257378, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4124026825319468311}, 'section': 'Section::::Abstract.'}]}]