Choose the BEST description of the chest's mechanical functions.

Choose the BEST description of the chest's mechanical functions.
A) The chest is a closed space with only one opening, the trachea, to inspire air; the diaphragm contracts down and the intercostal muscles expand the ribs, causing a negative pressure that fills the lungs with air.
B) With the chest being an airtight space, the act of breathing occurs when the muscles of the diaphragm and intercostal relax, which causes the lungs to expand and air to flow into the lungs.
C) The diaphragm contracts, causing the intercostal muscles that are attached to the lungs to also contract, which moves the air into the lungs.
D) The chest is a closed space, and the pleural space surrounds the lungs; when the diaphragm contracts and the intercostals expand, the chest and lungs move outward and downward, allowing expiration and gas exchange in the lungs.