Answer:
c. prevent each alveolus from collapsing as air moves in and out during respiration.
Step-by-step explanation:
In the lungs the exchange of gases takes place with the help of numerous tiny air sacs called alveoli. The alveoli collectively have large surface area which is required for efficient gas exchange. Surfactant is a complex of six lipids and four proteins that helps the alveoli to maintain their structure. It reduces surface tension at air-liquid interface within the lungs and make alveoli more stable. Without it the alveoli would collapse into each other during exhalation process which would form larger air sacs with smaller surface area. It is secreted by epithelial type II cells in alveolar space.
Babies born without sufficient surfactant face difficulty in breathing, become tired and do not get enough oxygen. They suffer from respiratory distress syndrome or hyaline membrane disease.