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': 'Monitoring of rate of occurrence of specific conditions to assess the stability or change in health levels of a population is known as: \nSelect and explain. \nA. Epidemiological surveillance, B. Active surveillance, C. Passive surveillance, D. Sentinel surveillance', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]