Solution: The cerebellum is the part of the human brain responsible for maintaining posture and balance. Located at the back of the brain, beneath the occipital lobes, it plays a crucial role in coordinating voluntary movements and ensuring smooth, balanced muscular activities. The cerebellum processes input from various sensory systems and integrates this information to fine-tune motor outputs, helping the body remain upright and stable. Therefore, the correct answer is the Cerebellum.