Question: who plays the role of black widow in avengers
[{'answer': 'Scarlett Johansson', 'provenance': [{'wikipedia_id': '709344', 'title': 'Black Widow (Natasha Romanova)', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 18, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]