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
Serial interval measures:(1997) 
Select and explain. 
A. Incubation period of disease, B. Sensitivity, C. Specificity, D. Positive predictive value
A: Incubation period of disease
Answer: A: Incubation period of disease 
Explanation: Ans: aRef: Park, 17th ed, p. 88 & 18th ed, p. 92