Question: who won the last 3 ncaa football championships
[{'answer': 'Alabama', 'provenance': [{'wikipedia_id': '17278765', 'title': 'College football national championships in NCAA Division I FBS', 'start_paragraph_id': 6, 'start_character': 510, 'end_paragraph_id': 6, 'end_character': 517, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'answer': 'Clemson'}]