Mark the correct pair of muscles involved in the normal breathing in humans.

Options

A. External and internal intercostal mus- cles
B. Diaphragm and abdominal muscles
C. Diaphragm and external intercostal mussles
D. Diaphragm and intercostal muscles

Answer

d

Explanation

During normal breathing 'only inspiration is an active process which is brought about by the diaphragm and external intercostal muscles. Normal expiration is a passive process which takes place by the recoil of the expanded lungs' and the relax- ation of the muscles of inspiration itself