All pure substances (1 point) *

a. contain only one type of atom

b. can be broken down into simpler substances

c. cannot be broken down into simpler compositions

d. have a fixed composition

What is the main difference between the central nervous system (cns) and the peripheral nervous system (pns)? .the cns involves the brain and spinal cord, and the pns involves the body nerves. the cns involves the body nerves, and the pns involves the brain and spinal cord. the cns involves sensory neurons, and the pns involves motor neurons. the cns involves motor neurons, and the pns involves sensory neurons.