Question: when did german bombers drop bombs on london
[{'answer': '1940 and 1941', 'provenance': [{'wikipedia_id': '112274', 'title': 'The Blitz', 'start_paragraph_id': 1, 'start_character': 59, 'end_paragraph_id': 1, 'end_character': 72, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '112274', 'title': 'The Blitz', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 784, 'bleu_score': 0.775688475801898, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8785734443271562321}, 'section': 'Section::::Abstract.'}]}]