Answer:The correct answer is A. brain stem.
Explanation:The brain stem is responsible for producing automatic behaviors necessary for survival. It controls essential functions such as breathing, heart rate, blood pressure, and basic motor functions. It serves as a bridge between the spinal cord and the higher brain structures and is involved in regulating various involuntary processes to maintain homeostasis. The brain stem also plays a crucial role in relaying sensory and motor signals between the brain and the rest of the body.