Answer,
The diaphragm contracts and moves lower and the chest cavity expands.
Explanation,
Inhalation is the process of breathing in.When you breath in the diaphragm contracts and moves downwards .This makes the spaces in the chest to expand and lungs increases in size.The air then enters the lungs to minimise the pressure in the lungs.The external intercostal muscles contract making the ribs to move outwards and inwards and they help to enlarge chest cavity.Diaphragm also separates heart and lungs from the abdomen.