The functional unit of the nervous system is the

The correct answer is C. Neurons.

A neuron is a specialized cell that processes and transmits information through electrical and chemical signals. Neurons are the basic units of the nervous system, and they are responsible for all of the brain’s functions, including thought, memory, emotion, and movement.

Nephrons are the functional units of the kidney. They are responsible for filtering the blood and producing urine.

Axons are long, slender projections that extend from the cell body of a neuron. They conduct electrical signals away from the cell body.

D is not the correct answer because it is not a single unit. It is a group of units.