The correct answer is B. Brain.
Cerebrospinal fluid (CSF) is a clear, colorless fluid that surrounds the brain and spinal cord. It helps to protect the brain and spinal cord from injury, and it also provides nutrients and removes waste products from the brain.
The heart is a muscular organ that pumps blood throughout the body. It is located in the chest, between the lungs. The liver is a large organ that is located in the upper right abdomen. It is responsible for many important functions, including digestion, metabolism, and detoxification. The kidneys are two bean-shaped organs that are located in the lower back. They are responsible for filtering waste products from the blood and producing urine.
Cerebrospinal fluid does not protect the heart, liver, or kidneys.