Question: where does the blood come from when on period
[{'answer': 'inner lining of the uterus', 'provenance': [{'wikipedia_id': '38203', 'title': 'Menstruation', 'start_paragraph_id': 1, 'start_character': 129, 'end_paragraph_id': 1, 'end_character': 155, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '38203', 'title': 'Menstruation', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 926, 'bleu_score': 0.972098488105909, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7575682279571007844}, 'section': 'Section::::Abstract.'}]}]