Question: who was the first african american elected to the united states senate
[{'answer': 'Hiram Rhodes Revels', 'provenance': [{'wikipedia_id': '21254073', 'title': 'List of African-American United States Senators', 'start_paragraph_id': 2, 'start_character': 142, 'end_paragraph_id': 2, 'end_character': 161, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '21254073', 'title': 'List of African-American United States Senators', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 1193, 'bleu_score': 0.9890406822930451, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7509664718100140493}, 'section': 'Section::::Abstract.'}]}]