Question: who developed the first alternating current electric system
[{'answer': 'Nikola Tesla', 'provenance': [{'wikipedia_id': '42986', 'title': 'Alternating current', 'start_paragraph_id': 61, 'start_character': 921, 'end_paragraph_id': 61, 'end_character': 933, 'bleu_score': 1.0, 'section': 'Section::::History.:Pioneers.\n'}]}, {'provenance': [{'wikipedia_id': '42986', 'title': 'Alternating current', 'start_paragraph_id': 61, 'start_character': 0, 'end_paragraph_id': 61, 'end_character': 1138, 'bleu_score': 0.988857503993915, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6259256085320533402}, 'section': 'Section::::History.:Pioneers.\n'}]}]