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: Social & Preventive Medicine
[{'content': 'Incidence is defined as - \nSelect and explain. \nA. Number of new cases occurring in a defined population, B. Total cases (new+old) occurring in a defined population, C. Number of exposed developing the disease in a defined population, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]