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': 'Serial interval is a measure of \nSelect and explain. \nA. Sensitivity, B. Specificity, C. Incubation period, D. Positive predictive value', 'role': 'user'}, {'content': "Answer: C \nExplanation: The gap in time between the onset of primary case and the secondary case is known as serial interval. By collecting information of the whole series of onset, we get a distribution of secondary cases from which we can guess the incubation period. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 108", 'role': 'assistant'}]