Answer:c. homeostasis
Explanation:homeostasis is the mechanism of the body to regulate and keep constant it's internal environment.
It usually involves a receptor which receives the stimuli,an intergration center which is usually the brain,and the effector.
Humans are warm blooded animals and so need to keep their body temperature constant regardless of that of the environment.
When it gets cold,the body shivers, Goosebumps appear and the hairs stands in attempts to keep the body warm
D. Can be found in the membrane, cytoplasm, or nucleus.
Enzymes don't take part in a reaction but just speeds up a reaction
