This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
All are true about Antigen drift EXCEPT? 
Select and explain. 
A. Its causes pandemic, B. Occurs due to mutation, C. Occurs frequently, D. Minor antigenic changes
A: Its causes pandemic
Answer: A: Its causes pandemic 
Explanation: Ans. (a) Its causes pandemicRef Jaweyz 24th ed ch-39