Question: who sings the theme song to happy days
[{'answer': 'Bill Haley and His Comets', 'provenance': [{'wikipedia_id': '39675028', 'title': 'Happy Days (TV theme)', 'start_paragraph_id': 2, 'start_character': 256, 'end_paragraph_id': 2, 'end_character': 281, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '39675028', 'title': 'Happy Days (TV theme)', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 709, 'bleu_score': 0.965400604802336, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2045621012238315794}, 'section': 'Section::::Abstract.'}]}]