Inhalation of air into the lungs is correctly described by which of the following? A. the action of the diaphragm and the ribs create a positive pressure in the thoracic cavity which causes air to move into the lungs. B. the volume of the thoracic cavity is increased as muscles relax, thus increas- ing the pressure and air is forced into the lungs. C. the thoracic cavity decreases in volume as muscles relax and pressure decreases so external air is forced into the lungs. D. the lungs expand as muscles contract, this creates a negative pressure so air is forced into the lungs.
Option D. The lungs expand as muscles contract, this creates a negative pressure so air is forced into the lungs.
