This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous Nervous System, Subject name: Physiology
The total volume of CSF is - 
Select and explain. 
A. 50 ml, B. 100 ml, C. 150 ml, D. 275 ml
C: 150 ml
Answer: C: 150 ml 
Explanation: Ans. is 'c' i.e., 150 ml o The major source of CSF is the choroidal plexus of all 4 ventricles, mainly in two lateral ventricles,o Other sources of CSF are ependymal cells of the ventricles and the brain itself, via perivascular spaces,o The total volume of CSF in an adult is about 125-150 ml.o The rate of formation of CSF is about 500-550 mi, day.o Thus the CSF is replaced 3-4 times every day.