**Core Concept**
Laryngomalacia is a condition characterized by the softening of the tissues of the larynx (voice box), leading to partial airway obstruction, particularly during inspiration. This condition is most commonly seen in infants and is a frequent cause of stridor in this age group.

**Why the Correct Answer is Right**
Stridor in infants is often caused by laryngomalacia due to the floppy nature of the supraglottic tissues, which can partially obstruct the airway during inspiration. This is due to the incomplete cartilaginous formation of the larynx, particularly the epiglottis and aryepiglottic folds, which are more prone to collapse. As a result, the airway is narrowed, and the child may exhibit stridor.

**Why Each Wrong Option is Incorrect**
**Option A:** Croup (laryngotracheobronchitis) is a common cause of stridor in children but is more often associated with an upper respiratory infection and typically presents with a barking cough. Laryngomalacia is a more common cause of stridor in infants.
**Option B:** Subglottic stenosis is a condition characterized by a narrowing of the airway below the vocal cords and is less common in infants. It is more often associated with trauma or prolonged intubation.
**Option C:** Vocal cord paralysis is a condition that can cause stridor, but it is relatively rare in infants and more often associated with neurological conditions.

**Clinical Pearl / High-Yield Fact**
Laryngomalacia is often associated with other conditions such as gastroesophageal reflux disease (GERD) and is more common in premature infants.

**Correct Answer:** C. Subglottic stenosis