This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
[{'content': 'Which of the following steps involved in formation of CSF? \nSelect and explain. \nA. Ultrafiltration and active secretion, B. Passive secretion, C. Active secretion and passive filtration, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ultrafiltration through fenestrated capillary walls Active secretion of ions and solutes Ref gk pal pg no 1157', 'role': 'assistant'}]