(20 13? Changde) is a schematic diagram of the chest and lungs. When the external intercostal muscle and diaphragm contract, the order of the three parts of pressure in the figure from large to small

(20 13? Changde) is a schematic diagram of the chest and lungs. When the external intercostal muscle and diaphragm contract, the order of the three parts of pressure in the figure from large to small is ( When the intercostal muscle contracts, the ribs lift up, the sternum moves upward and outward, and the left and right diameters and the up and down diameters of the thorax increase; The diaphragm also contracts, the top of the diaphragm drops, and the upper and lower diameters of the chest also increase. As a result, the volume of the chest cavity increases, and the air pressure in the chest cavity is lower than that in the lung, so the lung expands. At this time, the pressure in the lung is less than the external atmospheric pressure, and the external gas enters the lung to complete the inhalation action.

So choose: B.