The correct option is A Endolymph
Organ of Corti is a structure in the cochlea of the inner ear which produces nerve impulses in response to sound vibration. This spiral organ located at the cochlea in mammals is used as a receptor organ for hearing and is made up of epithelial cells and mechanosensory cells called hair cells that enables transduction of auditory signals into nerve impulses. Endolymph has a high positive potential and is a potassium rich fluid found in the basilar membrane.