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: Microbiology
The usual incubation period of pertussis is - 
Select and explain. 
A. 7-14 days, B. 3-5 days, C. 21-25 days, D. Less than 3 days
A: 7-14 days
Answer: A: 7-14 days 
Explanation: None