Question: when did the chicago bulls win their first championship
[{'answer': '1991', 'provenance': [{'wikipedia_id': '72866', 'title': 'Chicago Bulls', 'start_paragraph_id': 2, 'start_character': 218, 'end_paragraph_id': 2, 'end_character': 222, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '72866', 'title': 'Chicago Bulls', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 495, 'bleu_score': 0.903859127000134, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6321107484583183505}, 'section': 'Section::::Abstract.'}]}]