Question: who has held the office for chief minister for the longest time
[{'answer': 'Jyoti Basu', 'provenance': [{'wikipedia_id': '2382949', 'title': 'List of chief ministers of West Bengal', 'start_paragraph_id': 3, 'start_character': 106, 'end_paragraph_id': 3, 'end_character': 116, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]