Question: when were tractors first manufactured on a large scale
[{'answer': '1917', 'provenance': [{'wikipedia_id': '152692', 'title': 'Tractor', 'start_paragraph_id': 17, 'start_character': 214, 'end_paragraph_id': 17, 'end_character': 218, 'bleu_score': 1.0, 'section': 'Section::::History.:Gasoline-powered tractor.\n'}]}, {'provenance': [{'wikipedia_id': '152692', 'title': 'Tractor', 'start_paragraph_id': 17, 'start_character': 0, 'end_paragraph_id': 17, 'end_character': 524, 'bleu_score': 0.977139080690077, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15945830795737738389}, 'section': 'Section::::History.:Gasoline-powered tractor.\n'}]}]