Question: what type of coaster is the millennium force
[{'answer': 'steel', 'provenance': [{'wikipedia_id': '1491965', 'title': 'Millennium Force', 'start_paragraph_id': 1, 'start_character': 22, 'end_paragraph_id': 1, 'end_character': 27, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1491965', 'title': 'Millennium Force', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 681, 'bleu_score': 0.9386371051028921, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5395594732377182792}, 'section': 'Section::::Abstract.'}]}]