Question: how many schools have won a national championship in football
[{'answer': '7', 'provenance': [{'wikipedia_id': '17278765', 'title': 'College football national championships in NCAA Division I FBS', 'start_paragraph_id': 7, 'start_character': 728, 'end_paragraph_id': 7, 'end_character': 729, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '17278765', 'title': 'College football national championships in NCAA Division I FBS', 'start_paragraph_id': 64, 'start_character': 0, 'end_paragraph_id': 64, 'end_character': 1151, 'bleu_score': 0.9761989713904581, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4689366624097367642}, 'section': 'Section::::Poll era (1936–present).:Poll era national championships by school (1936–present).\n'}]}]