The answer is density-dependent factor
Think about skin cells. Skin cells shed every day, if cell division didn't take place, you would just constantly be losing skin cells.
The correct answer should be
<span>D. Autonomic nervous system
It is called autonomic because it works on its own and it regulates organs functioning which is a thing that happens involuntarily. It regulates heart beats for example and it's not something that you do voluntarily since the heart beats regardless of you. It also controls things like vomiting or sneezing that you can't choose not to do when it starts happening.</span>
