Which of the following does not occur during inhalation in mammals?

The correct answer is:

B. Diaphragm contracts and becomes dome shaped

During inhalation in mammals, several physiological changes occur to facilitate the intake of air into the lungs. The rib cage is raised up as the intercostal muscles (both external and internal intercostal muscles) contract, expanding the chest cavity. Simultaneously, the diaphragm contracts and moves downward, rather than becoming dome-shaped. This contraction of the diaphragm increases the vertical dimension of the thoracic cavity, which results in an increase in the overall volume of the thoracic cavity. As the volume of the thoracic cavity increases, the pressure within the cavity decreases (according to Boyle's law), creating a negative pressure relative to the outside atmosphere. This negative pressure gradient causes air to flow into the lungs, enabling inhalation. Therefore, option B is incorrect because the diaphragm flattens out when it contracts, rather than becoming dome-shaped.