Question: what is the fastest train in the us
[{'answer': 'The Acela Express'}, {'provenance': [{'wikipedia_id': '3663136', 'title': 'High-speed rail in the United States', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 522, 'bleu_score': 0.5627003419041411, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12710539008139840852}, 'section': 'Section::::Abstract.'}]}]