## **Core Concept**
The question assesses the understanding of normal and abnormal respiratory rates in infants, specifically those under 2 months old. Respiratory rate is a critical vital sign, and its elevation can indicate distress or disease. The World Health Organization (WHO) provides guidelines for fast breathing in children based on age.

## **Why the Correct Answer is Right**
Fast breathing in children under 2 months is defined by the WHO as a respiratory rate of 60 breaths per minute (bpm) or more. This threshold is crucial for identifying possible pneumonia or other severe infections in this vulnerable age group. The correct answer, , corresponds to this criterion.

## **Why Each Wrong Option is Incorrect**
* **Option A:** - This option suggests a much higher threshold, which is not the correct criterion for defining fast breathing in children under 2 months.
* **Option B:** - This option is lower than the established threshold for fast breathing in this age group.
* **Option D:** - This option does not align with the WHO's specified criteria for fast breathing in infants under 2 months.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the definition of fast breathing varies by age: 60 bpm or more for infants less than 2 months, 50 bpm or more for infants 2-12 months, and 40 bpm or more for children 1-5 years. This age-specific classification helps in the early detection of respiratory distress.

## **Correct Answer:** . 60 breaths per minute.