Question: who was the slave who sued for his freedom in the supreme court
[{'answer': 'Dred Scott', 'provenance': [{'wikipedia_id': '105817', 'title': 'Dred Scott', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 10, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]