Medulla oblongata is the part of hind brain and controls consciousness and arousal (the reticular formation) and its three vital reflex centres control the blood vessels diameter, heartbeat and breathing rate. This makes option A incorrect as medulla oblongata is not associated with sense of balance. The three semicircular canals lie at right angle to each other in vestibular apparatus of 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. This makes option B correct. Cerebrum is the part of fore brain and serves to receive sensory inputs, to bring about integration before commanding voluntary motor responses, to coordinate the activities of other part of brain, and to carry out higher thought processes for learning, memory, language and speech. This makes option C incorrect. Optic chiasma serves to send the data from right and left half of each retina to right and left visual area of cerebral cortex respectively
So, the correct answer is 'Semicircular canals'