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': 'Mad cow disease is due to - \nSelect and explain. \nA. Slow virus, B. Mycoplasma, C. Bacteria, D. F ungus', 'role': 'user'}, {'content': 'Answer: A \nExplanation: slow virus groupB causes mad cow disease REF:ANATHANARAYANAN MICROBIOLOGY NINTH EDITION PAGE.557', 'role': 'assistant'}]