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': 'Annual blood smear examination rate is an indicator of- \nSelect and explain. \nA. Disease rate (Prevalence), B. Operational efficiency, C. % of transmission of malaria, D. Infectivity rate', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]