Which of the following statements about the autonomic nervous system is not true?
a. it regulates the size of the pupilsb. all of the fibers are afferent fibersc. it consists of two subdivisionsd. it is an involuntary system

The statement B that says ''All of the fibers are afferent fibers'' is not true.

Explanation:

The autonomic or vegetative nervous system (ANS), also called neurovegetative or involuntary, is the part of the nervous system that is responsible for innervating the structures or organs related to the internal involuntary activities necessary for the functioning of the organism, such as the heart, the pupils , the glands among others.

It is considered mostly as an efferent system. Its efferent pathways are formed by two types of neurons, which are the preganglionic and postganglionic, and the synapse between these fibers, forms the autonomous ganglia. Afferent impulses range from visceral receptors, chemoreceptors, osmoreceptors and baroreceptors to the central nervous system.

Anatomically, it is divided into two autonomous nervous systems: the sympathetic and the parasympathetic. The functions of both are antagonistic, thus achieving a functional balance that tends to maintain body homeostasis. These divisions originate from the central nervous system and represent the efferent pathway through which it communicates with visceral effectors. The sympathetic nervous system increases energy expenditure against adverse conditions, dilates the pupil. The parasympathetic nervous system, prevents excessive energy expenditure, contracts the pupil.

from my research i have to the conclusion that decomposers, such as fungi, bacteria and invertebrates, play a critical role in nutrient cycling and without them the earth's ecosystem may not support life as we know it. elements such as carbon, nitrogen and phosphorus exist in limited amounts on earth, although huge amounts of carbon are being released into the atmosphere from underground sources now by humans. it is still extremely important that other nutrients be retained by the process of re-use. decomposers are organisms that are able to chemically break down dead material and make these elements available for use by other organisms. without this breakdown of dead material, dead bodies would pile up. so decomposers also play a role in clean up also. without them, life might not continue as we know it and dead material would overwhelm the earth.    

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.