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': 'Sentinel surveillance; TRUE is: \nSelect and explain. \nA. Data is itself reported to the health system, B. Active collection of data, C. Employed to identify the missing case, D. All of the above', 'role': 'user'}, {'content': "Answer: C \nExplanation: Surveillance:\xa0\n\nOngoing systematic collection, analysis & interpretation of data and use of this information to take action for prevention and control of disease.\xa0\nUsed for purpose of 'health planning'.\xa0\n\nTypes of Surveillance:", 'role': 'assistant'}]