This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'Fibronectin is used in periodontal therapy as \nSelect and explain. \nA. Growth factor, B. Bone graft, C. Biomodification of root surface, D. GTR membrane', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]