Question: who put the last spike in the transcontinental railroad
[{'answer': 'Leland Stanford', 'provenance': [{'wikipedia_id': '373929', 'title': 'Golden spike', 'start_paragraph_id': 1, 'start_character': 104, 'end_paragraph_id': 1, 'end_character': 119, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '373929', 'title': 'Golden spike', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 637, 'bleu_score': 0.9461462299376011, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14574147636213747830}, 'section': 'Section::::Abstract.'}]}]