Question

Infants are often referred to as belly breathers because

Answer 1

They breathe with their abdominal muscles.

Step-by-step explanation:

The abdominal muscles help the diaphragm pull downward to fill the lungs with air. Babies and young children will use their abdominal muscles much more to pull the diaphragm down for breathing. The intercostal muscles are not fully developed at the time of birth.

Answer 2

Either "they rely mostly on their diaphragm to breathe" or "their rib cage is less rigid and the ribs sit horizontally"

Depending on what choices you're given.