Answer:
O B. The diaphragm contracts and flattens.
Step-by-step explanation:
The diaphragm is a skeletal striated muscle that separates the abdominal cavity from the thoracic cavity, has a dome shape and plays a key role in breathing. Locate near the lumbar vertebrae, the lower ribs and the sternum and can be divided according to its location into three parts: sternal, costal and lumbar.
During inhalation, the diaphragm contracts and flattens, reducing the pressure inside the chest and compressing the viscera of the abdomen, which facilitates the entry of air into the lungs.
At the expiration, the inverse process occurs: it relaxes and rises, increasing the pressure inside the chest and expelling air from the lungs.