Question: when did the us bomb japan after pearl harbor
[{'answer': 'April 1942', 'provenance': [{'wikipedia_id': '68455', 'title': 'Bombing of Tokyo', 'start_paragraph_id': 2, 'start_character': 66, 'end_paragraph_id': 2, 'end_character': 76, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '68455', 'title': 'Bombing of Tokyo', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 378, 'bleu_score': 0.8611978723711351, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6982524722590541519}, 'section': 'Section::::Abstract.'}]}]