During Normal Exhalation,air Leaves the Lungs Because

During normal exhalation,air leaves the lungs because

A) air currents outside the body draw air out of the lungs in a process called transpiration.
B) the strong chest muscles force air out by squeezing the chest cavity and decreasing the air pressure inside the lungs.
C) the diaphragm and chest muscles relax,decreasing the volume of the chest cavity and making air pressure greater inside the lungs than outside so it flows outward.
D) there is more carbon dioxide inside the lungs than outside so air flows outward by diffusion.