Final answer:
The main muscles involved in pulmonary ventilation include the diaphragm, external intercostal muscles, and internal intercostal muscles, all contributing to the process of breathing.
Step-by-step explanation:
The main muscles of pulmonary ventilation are the diaphragm and the external intercostal muscles. These muscles play crucial roles in the processes of inspiration and expiration that make up the respiratory cycle. The diaphragm is a large, dome-shaped muscle that contracts and moves downward to expand the thoracic cavity, decreasing pressure and causing air to flow into the lungs. The external intercostal muscles assist by elevating the ribs, further expanding the thoracic cavity during inspiration. While the internal intercostal muscles are involved in expiration, especially during forced exhalation, they are not typically active during normal breathing. Therefore, the correct answer to the question is D. All of the above.