This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'CSF pressure is mainly regulated by \nSelect and explain. \nA. Rate of CSF formation, B. Rate of CSF absorption, C. Cerebral blood flow, D. Venous pressure', 'role': 'user'}, {'content': "Answer: B \nExplanation: Lumbar CSF pressure is normally 70 to 180 mm H2O. Up to pressures well above this range, the rate of CSF formation is independent of intraventricular pressure. However, absorption is propoional to the pressure Ref: Ganong's Review of Medical Physiology Twenty-Third Edition Page No:571", 'role': 'assistant'}]