Question: where does the blood from the superior vena cava come from
[{'answer': 'brachiocephalic vein'}, {'answer': 'azygos vein', 'provenance': [{'wikipedia_id': '242140', 'title': 'Superior vena cava', 'start_paragraph_id': 3, 'start_character': 285, 'end_paragraph_id': 3, 'end_character': 296, 'bleu_score': 1.0, 'section': 'Section::::Structure.\n'}]}]