Question: what is the main airport in london england
[{'answer': 'Heathrow', 'provenance': [{'wikipedia_id': '36098068', 'title': 'Airports of London', 'start_paragraph_id': 7, 'start_character': 11, 'end_paragraph_id': 7, 'end_character': 19, 'bleu_score': 1.0, 'section': 'Section::::International airports.:City (LCY).\n'}]}, {'provenance': [{'wikipedia_id': '36098068', 'title': 'Airports of London', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 710, 'bleu_score': 0.9410451604405151, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10168020094048054988}, 'section': 'Section::::International airports.:Heathrow (LHR).\n'}]}]