Because it produces sugar for humans and food for plants.
Number 3, CA cannot be an element, because it has 2 capital letters, meaning it contains 2 elements
The answer is reflexes. Reflexes are usually involuntary muscle movements that happen almost instantaneously in response to stimuli. A reflex is made possible by neural pathways called reflex arcs which can act on an impulse before that impulse reaches the brain. It is a survival mechanism evolved by the body used in the objective to escape danger.