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': 'Use of Doxycycline hyclate 20 mg. for a period of time forms \nSelect and explain. \nA. Prophylactic antimicrobial therapy, B. Systemic antimicrobial therapy, C. Host modulation therapy, D. Local drug delivery', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]