Question: who were the united states presidents that were assassinated
[{'answer': 'Abraham Lincoln', 'provenance': [{'wikipedia_id': '574536', 'title': 'List of United States presidential assassination attempts and plots', 'start_paragraph_id': 1, 'start_character': 337, 'end_paragraph_id': 1, 'end_character': 352, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'James A. Garfield', 'provenance': [{'wikipedia_id': '574536', 'title': 'List of United States presidential assassination attempts and plots', 'start_paragraph_id': 1, 'start_character': 361, 'end_paragraph_id': 1, 'end_character': 378, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'William McKinley', 'provenance': [{'wikipedia_id': '574536', 'title': 'List of United States presidential assassination attempts and plots', 'start_paragraph_id': 1, 'start_character': 387, 'end_paragraph_id': 1, 'end_character': 403, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'John F. Kennedy', 'provenance': [{'wikipedia_id': '574536', 'title': 'List of United States presidential assassination attempts and plots', 'start_paragraph_id': 1, 'start_character': 416, 'end_paragraph_id': 1, 'end_character': 431, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '574536', 'title': 'List of United States presidential assassination attempts and plots', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 612, 'bleu_score': 0.925309847846407, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8285971368951613564}, 'section': 'Section::::Abstract.'}]}]