Final answer:
The central nervous system is made up of the brain and spinal cord, which are distinct from other parts of the nervous system such as the parasympathetic and sympathetic nerves that belong to the peripheral nervous system.
Step-by-step explanation:
The central nervous system (CNS) encompasses two main subdivisions: the brain and spinal cord. Contrary to other components of the nervous system such as the parasympathetic nerves, spinal nerves, and sympathetic nerves, which are part of the peripheral nervous system (PNS), only the brain and spinal cord constitute the CNS. The PNS connects the central nervous system to the rest of the body, facilitating communication between the CNS and various body parts. Thus, the correct answer to what the central nervous system encompasses is 'a) Brain and spinal cord'.