Evaluating each option:
Cushioning the brain and spinal cord: CSF acts as a shock absorber, protecting the central nervous system.
Removing metabolic waste: CSF helps in the removal of waste products from the brain.
Transporting nutrients to the brain: CSF delivers essential nutrients to neural tissues.
Transmitting nerve impulses: Nerve impulses are transmitted by neurons through electrical and chemical signals, not by CSF.
Conclusion: The incorrect use of CSF among the options is transmitting nerve impulses.