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
Perilymph communicates with subarachnoid space through: 
Select and explain. 
A. Ductus reunions, B. Helicotrema, C. Utriculosaccular duct, D. Cochlear aqueduct
D: Cochlear aqueduct
Answer: D: Cochlear aqueduct 
Explanation: Ans: D (Cochlear aqueduct) Ref: Diseases of the Ear Nose and Throat by PL Dhingra 5th edn .2010.Page 12Explanation:* PerilymphComposition is like extracellular fluidLies between the bony and membranous labyrinthRich in Na+ ions* EndolymphFills the membranous labyrinth.It is rich in K~ ions.Composition is like intracellular fluid.Secreted by the stria vascularis of the crista and dark cells which are seen in the utricle and the ampullary ends of the semi circular canals.