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: Social & Preventive Medicine
Incubation period of influenza - 
Select and explain. 
A. 18 - 72 hrs, B. 1 - 6 hrs, C. 5 - 10 days, D. < 1 hrs
A: 18 - 72 hrs
Answer: A: 18 - 72 hrs 
Explanation: None