The correct option is D Partition of muscular septum separating the thoracic cavity from abdominal cavity
The diaphragm in the respiratory system is the dome shaped sheet of muscle that separates the chest from the abdomen. It is also referred to as the thoracic diaphragm because it is located in the thoracic cavity, or chest. It is attached to the spine, ribs and sternum and is the main muscle of respiration.