Question: what is the busiest station on the london underground
[{'answer': "King 's Cross St. Pancras", 'provenance': [{'wikipedia_id': '35110386', 'title': 'List of busiest London Underground stations', 'start_paragraph_id': 2, 'start_character': 38, 'end_paragraph_id': 2, 'end_character': 66, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '35110386', 'title': 'List of busiest London Underground stations', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 200, 'bleu_score': 0.9419661180380051, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 557079774028451763}, 'section': 'Section::::Abstract.'}]}]