Central nervous system consists of

The nervous system is organised into two anatomically and functionally distinct divisions: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). By definition, the CNS comprises the brain (protected within the skull) and the spinal cord (protected within the vertebral column) — the body's main processing and coordination centre. The PNS, in contrast, consists of the cranial and spinal nerves that carry signals between the CNS and the rest of the body.

The question asks specifically what the central nervous system is made up of. Applying the definition above: the CNS consists of exactly two structures — the brain and the spinal cord — which matches the option "brain and spinal cord."

• all organs — too broad: this groups in organs belonging to other body systems (e.g. muscular, digestive, glandular, respiratory) that are not part of the CNS.

• brain — names only one of the two CNS structures; incomplete on its own.

• spinal cord — names only one of the two CNS structures; incomplete on its own.

• brain and spinal cord — matches the complete anatomical definition of the CNS.