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': 'C.P.I.T.N is used in \nSelect and explain. \nA. Biggest population, B. Smallest population, C. Diagnostic tool, D. Screening purposes', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]