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: Physiology
[{'content': 'CSF is principally secreted by ? \nSelect and explain. \nA. Choroid plexus, B. Arachnoid granulation, C. Floor of fouh ventricle, D. Periaqueductal grey', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Choroid plexus', 'role': 'assistant'}]