This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'Which of the vaccine strain changed every year \nSelect and explain. \nA. Measles, B. Mumps, C. Influenza, D. Polio', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Influenza virus under goes antigenic shift and causes epidemics and pandemics. It requires vaccine strain also to be changed regularly Ref:- K Park 24th ed; pg num:- 164', 'role': 'assistant'}]