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': 'False about antigen drift - \nSelect and explain. \nA. Causes pandemic, B. Occurs due to mutation, C. Occurs more frequently, D. Affected by previous antibodies', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Repeated question please', 'role': 'assistant'}]