This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'The "risk of a disease" is measured by the - \nSelect and explain. \nA. Prevalence rate, B. Incidence rate, C. Case fatality rate, D. Communicability rate', 'role': 'user'}, {'content': 'Answer: B \nExplanation: <p> Incidence rate measures population at risk. Reference:Park&;s textbook of preventive and social medicine,K.Park,23rd edition,page no:60. <\\p>', 'role': 'assistant'}]