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': 'Commonest cause of sporadic encephalitis is: \nSelect and explain. \nA. Japanese B Virus, B. Herpes Simplex Virus, C. Human Immunodeficiency Virus, D. Rubeola Virus', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Answer is B (Herpes simplex encephalitis): The most common cause of sporadic viral encephalitis is HSV-1', 'role': 'assistant'}]