The graph shows how the volume of air in the lungs changes when a person is resting and breathing. Which processes are taking place to alter the volume at the point labelled X?
- AThe diaphragm is relaxing and the external intercostal muscles are relaxing.
- BThe diaphragm is contracting and the internal intercostal muscles are contracting.
- CThe diaphragm is contracting and the internal intercostal muscles are relaxing.
- DThe diaphragm is relaxing and the external intercostal muscles are contracting.