What deficiency causes a preterm infant respiratory distress syndrome?

A. Estrogen: Estrogen plays a role in fetal development and preparation for labor but is not directly responsible for preventing respiratory distress syndrome. Its levels do not determine lung maturity or surfactant production. B. Hyaline: Hyaline refers to the hyaline membranes seen in the lungs of infants with respiratory distress syndrome, not a deficiency. These membranes result from alveolar collapse and injury, not a causative factor. C. Protein: While protein is essential for overall growth and development, a general protein deficiency does not directly cause respiratory distress syndrome. Lung immaturity is related specifically to surfactant production. D. Surfactant: Respiratory distress syndrome occurs in preterm infants due to insufficient pulmonary surfactant, which reduces alveolar surface tension. Without adequate surfactant, alveoli collapse with each breath, leading to impaired gas exchange and respiratory difficulty.