This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2018, Subject name: Medicine
[{'content': "Differential diagnosis for 'thunderclap headache' are all except: \nSelect and explain. \nA. Encephalitis, B. Ischemic stroke, C. Subarachnoid hemorrhage, D. Meningitis", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Thunderclap Headache - Thunderclap headache is a severe headache that peaks within 60 seconds of onset, and its cause are: Subarachnoid hemorrhage: BERRY ANEURYSM Intracranial hypotension: DURAL ECTASIA / CSF Leak syndrome Reversible cerebral vasoconstriction syndrome Cervical aery dissection, Cerebral venous thrombosis Migraine Cluster headache Pituitary apoplexy', 'role': 'assistant'}]