This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: DNB 2018, Subject name: Social & Preventive Medicine
[{'content': 'Interval between primary and secondary case is called as:- \nSelect and explain. \nA. Serial interval, B. Generation time, C. Incubation period, D. Lead time', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The gap in time between the onset of the primary case and the secondary case is called "serial interval". Incubation period: The time interval between invasion by an infectious agent and appearance of the first sign or symptom of the disease in question. Generation time: interval of time between the receipt of infection by a host and maximal infectivity of that host Lead time: it is the advantage gained by screening, i.e. the period between diagnosis by early detection and diagnosis by other means.', 'role': 'assistant'}]