Question: where does the circle of willis supply blood to
[{'answer': 'the brain and surrounding structures', 'provenance': [{'wikipedia_id': '244346', 'title': 'Circle of Willis', 'start_paragraph_id': 1, 'start_character': 164, 'end_paragraph_id': 1, 'end_character': 200, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '244346', 'title': 'Circle of Willis', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 267, 'bleu_score': 0.8661072626070151, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2679834997476075741}, 'section': 'Section::::Abstract.'}]}]