The inner ear consists of two systems of canals which are namely cochlea and vestibular apparatus. The vestibular apparatus consists of three semicircular canals, cristae and two sacs called as saccule and utricle. The cochlea is the organ of hearing which contains mechanoreceptors for hearing. This makes option B incorrect. The three semicircular canals lie at the right angle to each other in vestibular apparatus of the inner ear and are filled with endolymph; this arrangement senses the change in movement (acceleration or deceleration) or position. The mechanism includes movement of cupula in response to movement of endolymph within the canal causing the bending of cilia to generate the nerve impulse. Hammer is one of the three ossicles of the middle ear which is concerned with amplification of air pressure while passing it from the inner surface of tympanic membrane via incus to stapes. The eustachian tube extends from each middle ear to nasopharynx and permits the equalization of air pressure. Thus, the correct answer is option A.