Question: who were the presidents that were assassinated while in office
[{'answer': 'John F. Kennedy', 'provenance': [{'wikipedia_id': '13434603', 'title': 'List of Presidents of the United States who died in office', 'start_paragraph_id': 3, 'start_character': 410, 'end_paragraph_id': 3, 'end_character': 425, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'William McKinley', 'provenance': [{'wikipedia_id': '13434603', 'title': 'List of Presidents of the United States who died in office', 'start_paragraph_id': 3, 'start_character': 46, 'end_paragraph_id': 3, 'end_character': 62, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'James A. Garfield', 'provenance': [{'wikipedia_id': '13434603', 'title': 'List of Presidents of the United States who died in office', 'start_paragraph_id': 2, 'start_character': 502, 'end_paragraph_id': 2, 'end_character': 519, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Abraham Lincoln', 'provenance': [{'wikipedia_id': '13434603', 'title': 'List of Presidents of the United States who died in office', 'start_paragraph_id': 2, 'start_character': 308, 'end_paragraph_id': 2, 'end_character': 323, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]