What organ is mainly responsible for coordinating movement?

The brain is primarily responsible for coordinating movement because it integrates sensory information and sends signals to various muscles throughout the body to produce coordinated actions. It processes input from the environment, such as visual and auditory cues, and makes decisions on how to respond through movement. The motor cortex, located in the brain, is specifically involved in planning and executing voluntary movements. Additionally, the cerebellum plays a crucial role in maintaining balance and fine-tuning movements, ensuring they are smooth and accurate.

The other organs, while essential for overall health and body functioning, have different primary responsibilities. The lungs are primarily involved in gas exchange, the heart is responsible for pumping blood throughout the body to supply oxygen and nutrients, and the liver plays a critical role in metabolism and detoxification. Thus, the brain's unique function in movement coordination makes it the correct choice.