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: Ans. (c) Incubation periodRef: Park textbook 22nd ed 196', 'role': 'assistant'}]