Question: when did the us buy land from mexico
[{'answer': '1848', 'provenance': [{'wikipedia_id': '448063', 'title': 'Mexican Cession', 'start_paragraph_id': 1, 'start_character': 147, 'end_paragraph_id': 1, 'end_character': 151, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '448063', 'title': 'Mexican Cession', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 618, 'bleu_score': 0.8646845385552061, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6378537839729659691}, 'section': 'Section::::Abstract.'}]}]