This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
[{'content': 'Which of the following is the best tool to measure communicability of an infection: \nSelect and explain. \nA. Prevalence rate, B. Primary attack rate, C. Secondary attack rate, D. Carrier rate', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. c. Secondary attack rateSecondary attack rate is useful to determine whether a disease of unknown etiology is communicable or not and in evaluating the effectiveness of control measures such as isolation and immunization.', 'role': 'assistant'}]