What is the primary function of the diaphragm during respiration?

The primary function of the diaphragm during respiration is to contract and create negative pressure in the thoracic cavity. When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity. This increase in cavity volume leads to a decrease in pressure relative to the atmospheric pressure, causing air to be drawn into the lungs. This process is essential for inhalation, as the negative pressure facilitates the flow of air into the lungs, allowing for the exchange of oxygen and carbon dioxide.

The other options, while related to the respiratory process, do not directly capture the primary role of the diaphragm. The action of contracting and creating negative pressure is fundamental to inhalation, which distinguishes it from the other listed functions.