Question: when did the air raids started in ww2
[{'answer': '7 September 1940', 'provenance': [{'wikipedia_id': '112274', 'title': 'The Blitz', 'start_paragraph_id': 2, 'start_character': 595, 'end_paragraph_id': 2, 'end_character': 611, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]