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': 'Not true regarding influenza virus is - \nSelect and explain. \nA. All types exhibit antigenic shift, B. Onlybtype A shows antigenic drift, C. Drift is accumulation of point mutations, D. None of the above', 'role': 'user'}, {'content': "Answer: A \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'}]