Answer: External intercoastal muscles increase the size of thorasic cavity during inhalation.
Step-by-step explanation:
Inhalation is the process of breathing in oxygen.
During inhalation, diaphragm contracts and it lead to the expansion of lung volume. When diaphragm contracts, it moves to the abdominal cavity which create a large thorasic cavity . when the external intercoastal muscles contracts, it cause toward and downward movement of the ribs, which cause the rib cage to expand , thereby leading to increase in size of thorasic cavity.