Question: by the 13th century the blank was the largest land empire at that point
[{'answer': 'Mongol Empire', 'provenance': [{'wikipedia_id': '10158', 'title': 'Empire', 'start_paragraph_id': 3, 'start_character': 533, 'end_paragraph_id': 3, 'end_character': 546, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '10158', 'title': 'Empire', 'start_paragraph_id': 41, 'start_character': 0, 'end_paragraph_id': 41, 'end_character': 533, 'bleu_score': 0.9766041382465441, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17063804966617882144}, 'section': 'Section::::History of imperialism.:Post-classical period.\n'}]}]