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
[{'content': 'All are true about Antigen drift EXCEPT? \nSelect and explain. \nA. Its causes pandemic, B. Occurs due to mutation, C. Occurs frequently, D. Minor antigenic changes', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Its causes pandemicRef Jaweyz 24th ed ch-39', 'role': 'assistant'}]