This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
[{'content': 'Most common cause of headache- \nSelect and explain. \nA. Tension headache, B. Migraine, C. Cluster headache, D. Trigemmal neuralgia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: *Common cause of primary headache is tension headache(69%). *Migraine(16%)and cluster headache(0.1%) Ref Harrison20th edition pg 1234', 'role': 'assistant'}]