Question: what breed of horses race in the kentucky derby
[{'answer': 'Thoroughbreds', 'provenance': [{'wikipedia_id': '17135', 'title': 'Kentucky Derby', 'start_paragraph_id': 1, 'start_character': 231, 'end_paragraph_id': 1, 'end_character': 244, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '17135', 'title': 'Kentucky Derby', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 318, 'bleu_score': 0.654705869701391, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6871734972251410224}, 'section': 'Section::::Abstract.'}]}]