Question: who was the chairman of the drafting committee of the constituent assembly
[{'answer': 'B.R. Ambedkar'}, {'provenance': [{'wikipedia_id': '1589530', 'title': 'Constituent Assembly of India', 'start_paragraph_id': 19, 'start_character': 0, 'end_paragraph_id': 19, 'end_character': 144, 'bleu_score': 0.7483293841345241, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8420642373247154463}, 'section': 'Section::::Organization.\n'}]}]