People are born with about 100 billion neurons, most of which are in the _________.

A) spinal cord
B) torso
C) heart
D) brain

Neurons

Nerve cells that are the basic building blocks of the nervous system, responsible for receiving, processing, and transmitting information through electrical and chemical signals.

Spinal Cord

A long, thin, tubular bundle of nervous tissue and support cells that extends from the brain down the length of the back, transmitting neural signals between the brain and the rest of the body.

Brain

The organ of the central nervous system in vertebrates located in the skull that is responsible for neural processing, including perception, emotions, thinking, and planning.