Question: what is the largest borough in alaska by population
[{'answer': 'Anchorage', 'provenance': [{'wikipedia_id': '87454', 'title': 'List of boroughs and census areas in Alaska', 'start_paragraph_id': 4, 'start_character': 209, 'end_paragraph_id': 4, 'end_character': 218, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]