This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'The most common cause of sporadic viral encephalitis is - \nSelect and explain. \nA. Japanese B encephalitis, B. Herpes simplex encephalitis, C. Human immunodeficiency virus encephalitis, D. Rubeola encephalitis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]