**Question:** MC cause of intermittent stridor in a 10 days old child is:

A. Foreign body aspiration
B. Congenital laryngomalacia
C. Foreign body aspiration
D. Bronchial wall inflammation (bronchiolitis)

**Core Concept:**
The correct answer is related to the identification of a common cause of intermittent stridor in infants, specifically in a 10 days old child. Stridor is a high-pitched, wheezing sound produced during inspiration due to narrowing of the airway. In this context, we need to consider the most likely cause among the provided options.

**Why the Correct Answer is Right:**
In this case, the correct answer is **B. Congenital laryngomalacia**, also known as floppy larynx syndrome. Laryngomalacia is a common cause of intermittent stridor in infants, particularly in those aged around 10 days. The larynx is the small, horseshoe-shaped cartilaginous structure in the neck that forms the entrance to the trachea and the upper airway. In congenital laryngomalacia, the cartilage in the larynx becomes weakened or thin, leading to collapse of the posterior or aryepiglottic folds during inspiration, causing narrowing of the airway and stridor.

**Why Each Wrong Option is Incorrect:**

**A.** Foreign body aspiration: Although foreign body aspiration can cause stridor, it is less common in infants under the age of 6 months. This option is less likely in a 10-day-old infant.

**C.** Foreign body aspiration: Similar to option A, this option is less specific to the age group mentioned in the question. Foreign body aspiration is more common in older children and adults.

**D.** Bronchial wall inflammation (bronchiolitis): Bronchiolitis is characterized by inflammation of the bronchioles, leading to respiratory distress. However, this condition is not specific to the age group mentioned in the question, and it primarily affects infants under 1 year of age.

**Explanation of the Core Concept:**
The main focus of this question is to understand the most common cause of intermittent stridor in a 10-day-old infant, which can help in arriving at the correct diagnosis and appropriate management.

**Why the Correct Answer is Right:**
The correct answer, **B. Congenital laryngomalacia**, is the most appropriate cause of intermittent stridor in a 10-day-old infant. Congenital laryngomalacia is a congenital anomaly affecting the larynx, which leads to collapse of the aryepiglottic folds during inspiration, causing stridor. This condition commonly presents in infants around 1 month of age, making it an appropriate cause for an 10-day-old infant.

**Why Each Wrong Option is Incorrect:**

**A.** Foreign body aspiration: As mentioned earlier, foreign body aspiration is a less common cause of stridor in very