**Core Concept**
Inspiratory stridor is a high-pitched sound heard during inspiration, resulting from turbulent airflow through a partially obstructed airway. This condition often arises from lesions or abnormalities in the upper airway, where the airway diameter is smaller and more susceptible to obstruction.

**Why the Correct Answer is Right**
Supraglottic lesions, which occur above the glottis (the opening between the vocal cords), can cause inspiratory stridor. This is because the supraglottic region has a relatively narrow diameter, making it prone to obstruction by lesions or edema. The narrowed airway during inspiration creates turbulence, producing the characteristic high-pitched sound of stridor. The supraglottic area includes structures such as the epiglottis, arytenoids, and false vocal cords, which can be affected by lesions, inflammation, or tumors.

**Why Each Wrong Option is Incorrect**
**Option B:** Subglottic lesions, located below the glottis, typically cause biphasic or expiratory stridor, rather than inspiratory stridor. This is due to the larger diameter of the subglottic airway, which is less susceptible to obstruction during inspiration.
**Option C:** Tracheal lesions can cause stridor, but the type of stridor depends on the location and severity of the lesion. Tracheal lesions more commonly cause biphasic or expiratory stridor, rather than inspiratory stridor specifically.
**Option D:** Bronchus lesions are less likely to cause stridor, as the bronchi are larger and more distal in the airway, making them less susceptible to obstruction during inspiration.

**Clinical Pearl / High-Yield Fact**
Remember that the location of upper airway lesions determines the type of stridor: supraglottic lesions cause inspiratory stridor, subglottic lesions cause biphasic or expiratory stridor, and tracheal lesions can cause biphasic or expiratory stridor.

**✓ Correct Answer: A. Supraglottic**