Question: when were horses first introduced to north america
[{'answer': 'the 16th century', 'provenance': [{'wikipedia_id': '46694871', 'title': 'Horses in the United States', 'start_paragraph_id': 2, 'start_character': 147, 'end_paragraph_id': 2, 'end_character': 163, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '46694871', 'title': 'Horses in the United States', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 242, 'bleu_score': 0.825918264509606, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11310165209708316086}, 'section': 'Section::::Abstract.'}]}]