Question: what does ccf stand for in the air force
[{'answer': 'First Sergeant', 'provenance': [{'wikipedia_id': '20098974', 'title': 'List of U.S. Air Force acronyms and expressions', 'start_paragraph_id': 235, 'start_character': 18, 'end_paragraph_id': 235, 'end_character': 32, 'bleu_score': 1.0, 'section': 'Section::::C.\n'}]}]