Question: where does most of the us electricity come from
[{'answer': 'fossil fuels', 'provenance': [{'wikipedia_id': '7635170', 'title': 'Energy in the United States', 'start_paragraph_id': 4, 'start_character': 31, 'end_paragraph_id': 4, 'end_character': 43, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'petroleum', 'provenance': [{'wikipedia_id': '7635170', 'title': 'Energy in the United States', 'start_paragraph_id': 4, 'start_character': 114, 'end_paragraph_id': 4, 'end_character': 123, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'coal', 'provenance': [{'wikipedia_id': '7635170', 'title': 'Energy in the United States', 'start_paragraph_id': 4, 'start_character': 134, 'end_paragraph_id': 4, 'end_character': 138, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'natural gas', 'provenance': [{'wikipedia_id': '7635170', 'title': 'Energy in the United States', 'start_paragraph_id': 4, 'start_character': 153, 'end_paragraph_id': 4, 'end_character': 164, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]