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 antigenic drift - \nSelect and explain. \nA. Occur under pressure for immunity, B. Responsible for epidemics of influenza, C. Occurs only in influenza-A, D. Occur every 10-12 years', 'role': 'user'}, {'content': "Answer: C \nExplanation: Antigenic drift the gradual sequential change in antigenic structure occurring regularly at frequent intervals. Antigenic drift is due to mutation and selection. It accounts for the periodic epidemics of influenza. REF:ANANTHANARAYAN AND PANIKER'S TEXTBOOK OF MICROBIOLOGY 9TH EDITION PAGE NO-499", 'role': 'assistant'}]