Explanation:
The correct answer is E: medulla.

Explanation:
The medulla oblongata, located in the brainstem, is responsible for controlling involuntary functions such as breathing, heart rate, and blood pressure. It contains centers that regulate the rate and depth of breathing in response to the levels of carbon dioxide in the blood, helping to maintain homeostasis in the body.

Here’s why the other options are not correct:
- A. Cerebrum: Responsible for higher functions like thought, memory, and voluntary movements, not the regulation of breathing.
- B. Olfactory lobe: Involved in the sense of smell.
- C. Pituitary organ: The pituitary gland is a hormone-secreting gland and is not involved in breathing regulation.
- D. Cerebellum: Controls coordination and balance, not respiratory functions.

Therefore, medulla is the center that controls respiratory activities in mammals.