Question: who played darth vader in star wars 4
[{'answer': 'David Prowse', 'provenance': [{'wikipedia_id': '53862', 'title': 'Darth Vader', 'start_paragraph_id': 24, 'start_character': 41, 'end_paragraph_id': 24, 'end_character': 53, 'bleu_score': 1.0, 'section': 'Section::::Creation and development.:Portrayals.\n'}]}]