The correct answer is option 'D', the medulla oblongata.

The medulla oblongata is a part of the brainstem that is responsible for controlling many vital involuntary functions, including breathing. It is located at the base of the brain, just above the spinal cord. The medulla oblongata contains a respiratory center that regulates the rate and depth of breathing.

The medulla oblongata controls breathing through a process called respiratory control. This process involves the coordination of various muscles and nerves to ensure the proper intake of oxygen and removal of carbon dioxide from the body.

Here is a detailed explanation of how the medulla oblongata controls breathing:

1. Respiratory center: The medulla oblongata contains two main areas that form the respiratory center - the dorsal respiratory group (DRG) and the ventral respiratory group (VRG). The DRG is responsible for initiating inspiration, while the VRG assists in both inspiration and expiration.

2. Chemoreceptors: The medulla oblongata has specialized receptors called chemoreceptors that detect changes in the levels of oxygen, carbon dioxide, and pH in the blood. When the chemoreceptors sense an increase in carbon dioxide or a decrease in oxygen levels, they send signals to the respiratory center to increase the rate and depth of breathing.

3. Nerve impulses: The respiratory center in the medulla oblongata generates nerve impulses that travel along the phrenic nerves to the diaphragm and intercostal nerves to the intercostal muscles. These impulses stimulate the contraction of the diaphragm and intercostal muscles, leading to inspiration.

4. Rhythmicity center: The medulla oblongata also contains a rhythmicity center that helps establish the basic rhythm of breathing. It generates regular impulses that coordinate the timing of inspiration and expiration.

5. Feedback mechanism: The medulla oblongata receives feedback from various receptors in the body, such as the stretch receptors in the lungs and the proprioceptors in the muscles and joints. This feedback helps to regulate the depth and rate of breathing according to the body's needs.

In summary, the medulla oblongata plays a crucial role in controlling breathing by regulating the rate and depth of respiration. It receives input from chemoreceptors and other feedback mechanisms to ensure the body's respiratory needs are met.