This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Anatomy
The cerebrospinal fluid 
Select and explain. 
A. 10% of it drain to cerebral lymphatics, B. Formed by choroid plexus mostly, C. Mostly found in skull bones than in spine, D. Through aqueduct passes from lateral ventricle to 3rd ventricle
B: Formed by choroid plexus mostly
Answer: B: Formed by choroid plexus mostly 
Explanation: The cerebrospinal fluid is a modified tissue fluid. It is contained in the ventricular system of the brain and in the subarachnoid space around the brain and spinal cord. The bulk of cerebrospinal fluid is formed by the choroid plexuses of the lateral ventricles and lesser amounts by the choroid plexuses of third and fouh ventricles Ref BDC volume3,6th edition pg 331