Final answer:
Nasal flaring is a sign of dyspnea specific to infants, often seen in cases such as Respiratory Distress Syndrome (RDS) associated with premature birth and insufficient surfactant production.
Step-by-step explanation:
One sign of dyspnea specific to infants is B. Nasal flaring. This is a distinctive sign that an infant is having difficulty breathing. In the context of a premature baby, before the production of enough pulmonary surfactant by type II cells, one might expect the infant to have difficulty inflating the lungs. This condition is known as Respiratory Distress Syndrome (RDS), which can lead to symptoms such as gasping, grunting during exhalation, and nasal flaring, as the infant makes an increased effort to breathe.