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
CSF is principally secreted by ? 
Select and explain. 
A. Choroid plexus, B. Arachnoid granulation, C. Floor of fouh ventricle, D. Periaqueductal grey
A: Choroid plexus
Answer: A: Choroid plexus 
Explanation: A i.e. Choroid plexus