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
Major epidemics are due to antigenic drift 
Select and explain. 
A. Asymptomatic seen rarely, B. Incubation period 10-12 hrs, C. All ages and sex equally affected, D. Pandemic rare
C: All ages and sex equally affected
Answer: C: All ages and sex equally affected 
Explanation: None