Question: who served as head of the us sanitary commission
[{'answer': 'Henry Whitney Bellows', 'provenance': [{'wikipedia_id': '3509373', 'title': 'United States Sanitary Commission', 'start_paragraph_id': 1, 'start_character': 480, 'end_paragraph_id': 1, 'end_character': 501, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '3509373', 'title': 'United States Sanitary Commission', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 450, 'bleu_score': 0.970795021215021, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17442855556234739017}, 'section': 'Section::::History.\n'}]}]