Question: where does the umbilical vein enter the circulation of the fetus
[{'answer': 'the portal vein', 'provenance': [{'wikipedia_id': '3046797', 'title': 'Fetal circulation', 'start_paragraph_id': 5, 'start_character': 354, 'end_paragraph_id': 5, 'end_character': 369, 'bleu_score': 1.0, 'section': 'Section::::Structure.\n'}]}, {'provenance': [{'wikipedia_id': '3046797', 'title': 'Fetal circulation', 'start_paragraph_id': 5, 'start_character': 0, 'end_paragraph_id': 5, 'end_character': 1017, 'bleu_score': 0.9748696792430981, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4702714927365945711}, 'section': 'Section::::Structure.\n'}]}]