Respiratory movement refers to the rhythmic expansion and contraction of the human chest, including inhalation and exhalation. When inhaling and the intercostal muscles contract, the ribs move upward and outward, which increases the anterior-posterior diameter and left-right diameter of the chest cavity.

At the same time, the diaphragm contracts and the top of the diaphragm descends, which increases the upper and lower diameter of the thorax, increases the volume of the thorax, and expands the lung, so that the air pressure in the lung is lower than the external atmospheric pressure, and the external air enters the lung through the respiratory tract to complete inhalation. On the contrary, it can be seen that option B is correct.

So choose B.