Concept:Exhalation is the process of breathing out, caused by relaxation of the respiratory muscles after inhalation.
Explanation:During exhalation, the diaphragm relaxes and moves upward, returning to its dome-shaped position.
It does not flatten during exhalation.
Flattening of the diaphragm occurs only during inhalation, when it contracts and moves downward.
As the diaphragm relaxes, the thoracic cavity decreases in volume.
The ribs move downward and inward due to relaxation of the intercostal muscles.
This decrease in volume causes the air pressure inside the thoracic cavity to increase.
Higher pressure inside forces air out of the lungs.
Therefore, the action that does not occur during exhalation is the flattening of the diaphragm.
Answer:B. Diaphragm flattens