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: Pathology
[{'content': 'Cause of essential (Primary) Hypertension is: \nSelect and explain. \nA. Excessive sympathetic nervous system activity, B. Renal artery stenosis., C. Glomerulonephritis., D. Chronic Renal failure.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]