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': 'Best tool to measure communicability of an infectious disease? \nSelect and explain. \nA. Secondary attack rate, B. Generation timeSerial interval, C. Serial interval, D. Incubation period', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e., Secondary attack rate Secondary attack rateSAR is defined as "the number of exposed persons developing the disease within the range of incubation period, following exposure to primary case.', 'role': 'assistant'}]