Question: who is the actor who plays iron man
[{'answer': 'Downey Jr.', 'provenance': [{'wikipedia_id': '171045', 'title': 'Robert Downey Jr.', 'start_paragraph_id': 0, 'start_character': 7, 'end_paragraph_id': 0, 'end_character': 17, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]