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': 'Communicability of disease is assessed by \nSelect and explain. \nA. Secondary attack rate, B. Generation time, C. Serial interval, D. Incubation period', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]