Question: who played the role of thad on gunsmoke
[{'answer': 'Ewing', 'provenance': [{'wikipedia_id': '20995097', 'title': 'Roger Ewing', 'start_paragraph_id': 0, 'start_character': 6, 'end_paragraph_id': 0, 'end_character': 11, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '20995097', 'title': 'Roger Ewing', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 252, 'bleu_score': 0.948006874591591, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10283212080734044830}, 'section': 'Section::::Biography.\n'}]}]