Question: who is the actor who plays bucky barnes
[{'answer': 'Sebastian Stan', 'provenance': [{'wikipedia_id': '9110929', 'title': 'Sebastian Stan', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 14, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]