Which two parts make up the nervous system?

The correct choice highlights the two main divisions of the nervous system: the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system consists of the brain and spinal cord, which serve as the primary control center for processing and transmitting information throughout the body. The peripheral nervous system, on the other hand, encompasses all the nerves that branch out from the CNS and extend to various parts of the body, linking the CNS to limbs and organs. This division is fundamental because it allows for the coordination of voluntary and involuntary actions, as well as the communication between the brain, spinal cord, and the rest of the body.

The other choices represent subdivisions or components of the nervous system but do not encompass the entire structure. For instance, while the sympathetic and parasympathetic nervous systems are parts of the autonomic system that manage involuntary bodily functions, they are not standalone categories of the nervous system. Similarly, the autonomic and somatic nervous systems pertain to the types of control exerted over bodily functions, but they do not describe the overall framework of the nervous system like the CNS and PNS do. Thus, A is the best answer as it directly identifies the two primary components of the nervous system.