Question: where does urea come from in the body
[{'answer': 'The liver', 'provenance': [{'wikipedia_id': '31734', 'title': 'Urea', 'start_paragraph_id': 2, 'start_character': 397, 'end_paragraph_id': 2, 'end_character': 406, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '31734', 'title': 'Urea', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 632, 'bleu_score': 0.9344132766918241, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17136865529149473225}, 'section': 'Section::::Abstract.'}]}]