Question: who was the original host of american top 40 music countdown
[{'answer': 'Casey Kasem', 'provenance': [{'wikipedia_id': '596708', 'title': 'American Top 40', 'start_paragraph_id': 1, 'start_character': 133, 'end_paragraph_id': 1, 'end_character': 144, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '596708', 'title': 'American Top 40', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 559, 'bleu_score': 0.9682494507378011, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3463595389685074480}, 'section': 'Section::::Abstract.'}]}]