Question: who played benjamin button as an old man
[{'answer': 'Brad Pitt', 'provenance': [{'wikipedia_id': '8031432', 'title': 'The Curious Case of Benjamin Button (film)', 'start_paragraph_id': 1, 'start_character': 245, 'end_paragraph_id': 1, 'end_character': 254, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]