Question: who sings the opening for nascar on nbc
[{'answer': 'Metallica', 'provenance': [{'wikipedia_id': '4073204', 'title': 'NASCAR on NBC', 'start_paragraph_id': 19, 'start_character': 4, 'end_paragraph_id': 19, 'end_character': 13, 'bleu_score': 1.0, 'section': 'Section::::History.:Original run (2001–2006).:Music.\n'}]}, {'answer': 'Blake Shelton', 'provenance': [{'wikipedia_id': '4073204', 'title': 'NASCAR on NBC', 'start_paragraph_id': 52, 'start_character': 130, 'end_paragraph_id': 52, 'end_character': 143, 'bleu_score': 1.0, 'section': 'Section::::History.:NASCAR returns to NBC.:Music and graphics.\n'}]}, {'answer': 'ZZ Ward', 'provenance': [{'wikipedia_id': '4073204', 'title': 'NASCAR on NBC', 'start_paragraph_id': 52, 'start_character': 388, 'end_paragraph_id': 52, 'end_character': 395, 'bleu_score': 1.0, 'section': 'Section::::History.:NASCAR returns to NBC.:Music and graphics.\n'}]}]