**Core Concept**
Congenital laryngeal stridor, also known as laryngomalacia, is a condition characterized by the softening of the cartilaginous structures of the larynx, leading to partial airway obstruction during inspiration. This condition is often associated with a high-pitched inspiratory stridor.

**Why the Correct Answer is Right**
Laryngomalacia is caused by the softening of the posterior cricoid cartilage and the arytenoid cartilages, which can lead to partial collapse of the airway during inspiration. The exact mechanism is not fully understood, but it is believed to be related to the incomplete development of the cartilaginous structures. The condition is often associated with other congenital anomalies, such as cardiac defects and gastroesophageal reflux disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe congenital laryngeal stridor. A laryngeal web is a different condition characterized by a web-like structure that can form in the larynx.
**Option B:** This option is incorrect because it is a different condition that affects the trachea, not the larynx.
**Option C:** This option is incorrect because it refers to a condition that affects the nasal passages, not the larynx.

**Clinical Pearl / High-Yield Fact**
Laryngomalacia is the most common cause of congenital stridor, and it often presents with a high-pitched inspiratory stridor that worsens with agitation or feeding. It is essential to differentiate it from other conditions that can cause stridor, such as vocal cord paralysis or a laryngeal tumor.

**Correct Answer: D. Laryngomalacia**