Explanation:
Very young children tend to breathe predominantly with their diaphragm because:
c. their intercostal muscles are not fully developed.
Intercostal muscle are located between the ribs and helps in the movement with of the chest. These help in increasing the volume of the chest and are mainly associated with the breathing. Young childrens do not have very well developed intercostal muscle and so they use their diaphragm to breathe.
