The correct answer is the peripheral nervous system.
In vertebrates, there are two main parts of the nervous system, that is, the central nervous system and the peripheral nervous system. The central nervous system comprises of the spinal cord and the brain.
On the other hand, the peripheral nervous system comprises basically of nerves that are bounded bundles of axons or long fibers, which associate the central nervous system to each part of the body.
Hierachy is a series of ordered groupings
Comparative and experimental investigations are two of three scientific investigations, the other is descriptive investigations.
--hope this helps--
C.stressors are activities that can cause danger
D oxygen there was no free oxygen on the earth
