Under-production of pulmonary surfactant in IRDS leads to decreased compliance of alveolar tissue. Based upon this information, which of the following must be true regarding pulmonary surfactant?
A. Its adsorption to the water-alveolar interface increases surface tension, preventing alveolar collapse due to intra-thoracic pressure.
B. Its absence decreases the minimum radial size of alveoli able to avoid collapse at a given pressure of inspired air.
C. Its adsorption to the water-alveolar interface decreases surface tension, decreasing the pressure difference required to inflate the airway.
D. Its presence increases the efficiency of gas exchange across the alveolar membrane by decreasing the surface area of the alveolus at a given pressure of inspired air.

IRDS (Infantile respiratory distress syndrome) is the syndrome shown by the newborn or premature infants. This mainly occur due to the deficiency of the pulmonary surfactant.

The main function of the pulmonary surfactant is the increase in the expand ability of the lungs and prevent the lungs collapsing. The pulmonary surfactant decreases the surface tension and also reduces the pressure difference required for the inflation.

Thus, the correct answer is option (C).