The correct option is A Vestibular apparatus
The vestibular is the organ of equilibrium. The vestibular’s function is to register the body's movements, thus ensuring that we can keep our balance.
The ear ossicles are small flexible chain of three small bones - the malleus (hammer shaped), the incus (anvil shaped) and the stapes (stirrup shaped). They transmit and amplify sound waves across the tympanic cavity from the tympanic membrane to the oval window.
The Eustachian tube, also known as the auditory tube or pharyngotympanic tube, a part of the middle ear is a tube that links the nasopharynx to the middle ear.
The organ of Corti is the sensitive element in the inner ear and can be thought of as the body's microphone. It is situated on the basilar membrane in one of the three compartments of the Cochlea. It contains four rows of hair cells which protrude from its surface.