Organ of corti is situated in -

Ans. is 'a' i.e., Basilar membrane o Scala media (cochlear duct or membranous labyrinth) has 3 walls : -The basilar membrane, which supports the organ of corti.The Reissner's membrane which separates it from the scala vestibuli.The stria vascularis which contains vascular epithelium and is concerned with secretion of endolymph.