This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
CSF is similar to 
Select and explain. 
A. Endolymph, B. Perilymph, C. Coilymph, D. Urine
B: Perilymph
Answer: B: Perilymph 
Explanation: Perilymph resembles extracellular fluid and rich in Na ions. It communicates with CSF through aqueduct of the cochlea which opens into scala tympani near the round window. Reference: Dhingra 6th edition.