What happens to the pressure in the chest cavity during inhalation?

During inhalation, the diaphragm and intercostal muscles contract, expanding the thoracic cavity. This expansion increases the volume of the chest cavity, which causes a decrease in the pressure within the thoracic cavity compared to the outside atmospheric pressure. As the pressure inside the chest cavity drops, air is drawn into the lungs to equalize the pressure, facilitating the process of breathing. The decrease in pressure is essential for allowing air to flow freely into the lungs, making this the correct answer.