Question: when did the movie never back down come out
[{'answer': 'March 14 , 2008', 'provenance': [{'wikipedia_id': '18640429', 'title': 'Never Back Down', 'start_paragraph_id': 1, 'start_character': 166, 'end_paragraph_id': 1, 'end_character': 181, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]