During inspiration, the space inside the chest cavity is increased due to:

Explanation

Option A occurs during expiration, as the diaphragm's muscles relax, causing the chest cavity space to decrease and the air is pushed out.Option B also occurs during expiration, as in inspiration, the external intercostal muscles contract while the inner ones relax, and in expiration, the external intercostal muscles relax and inner ones contract.Option C occurs during expiration, as the volume of the chest cavity decreases, causing an increase in pressure which drives the movement of air back into the atmosphere. The reverse process occurs in inspiration.Option D occurs during inspiration, as the diaphragm muscles contract, causing the diaphragm to flatten. This increases the volume of the chest cavity (along with the external intercostal muscles, contracting, and inner ones, relaxing, resulting in the ribcage, moving upwards and outwards), which causes a decrease in pressure, resulting in the movement of air into the lungs from the atmosphere.