The correct answer is option 3, Cerebellum equilibrium. The sense of balance is achieved through the coordination and processing of sensory information by the cerebellum. The cerebellum is responsible for receiving information from the inner ear, vision, and proprioception (sensing the position and movement of the body). It processes this information to maintain balance and coordinate smooth movements. The cerebrum, as mentioned in option 1, is not directly involved in maintaining balance but plays a role in higher cognitive functions. The thalamus, mentioned in option 2, is responsible for relaying sensory information to the appropriate areas of the brain, but not specifically for balance. The spinal cord, mentioned in option 4, is primarily responsible for transmitting sensory and motor information between the brain and body, not specifically for balance.