The femur is not part of the circulatory system because it is a bone.
The organ that removes water, salts and other wastes from you blood is (d) the Kidney
Cerebrospinal fluid (CSF), clear, colourless liquid that fills and surrounds the brain and the spinal cord and provides a mechanical barrier against shock. Formed primarily in the ventricles of the brain, the cerebrospinal fluid supports the brain and provides lubrication between surrounding bones and the brain and spinal cord. When an individual suffers a head injury, the fluid acts as a cushion, dulling the force by distributing its impact. The fluid helps to maintain pressure within the cranium at a constant level.
https://www.britannica.com/science/cerebrospinal-fluid
