The answer is that Both aid in the expansion and relaxation of lungs. Diaphragm and the rib muscles are vital in the breathing process. During inhalation the intercostal muscles contract, expanding the ribcage, the diaphragm contracts, pulling downwards to increase the volume of the chest, pressure inside the chest is lowered and air is sucked into the lungs. During exhalation the intercostal muscles relax, the ribcage drops inward and downwards, the diaphragm relaxes, moving back upwards, decreasing the volume of the chest, the pressure inside the chest increases and air is forced out.
The answer is A, just took the test on edge
