Question: what are the 4 types of blood vessels
[{'answer': 'arteries', 'provenance': [{'wikipedia_id': '48530', 'title': 'Blood vessel', 'start_paragraph_id': 2, 'start_character': 43, 'end_paragraph_id': 2, 'end_character': 51, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'capillaries', 'provenance': [{'wikipedia_id': '48530', 'title': 'Blood vessel', 'start_paragraph_id': 2, 'start_character': 116, 'end_paragraph_id': 2, 'end_character': 127, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'veins', 'provenance': [{'wikipedia_id': '48530', 'title': 'Blood vessel', 'start_paragraph_id': 2, 'start_character': 234, 'end_paragraph_id': 2, 'end_character': 239, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]