**Question:** Normal body mass index is-

A. 20-25
B. 25-30
C. 18.5-24.9
D. 30-35

**Core Concept:**
The body mass index (BMI) is a mathematical index used to categorize an individual's weight in relation to their height. It is calculated by dividing an individual's weight in kilograms by the square of their height in meters (kg/m^2). The World Health Organization (WHO) has defined normal BMI ranges based on the distribution of BMI in the general population.

**Why the Correct Answer is Right:**
The correct answer is 18.5-24.9 because this range represents the normal BMI according to the WHO classification. BMI within this range indicates a healthy weight for an individual of a given height. BMI values below 18.5 are considered underweight, while those above 24.9 are considered overweight or obese.

**Why Each Wrong Option is Incorrect:**
A) 20-25: This range is slightly higher than the normal BMI and may be considered overweight.
B) 25-30: This range is within the overweight category, not specifically addressing the normal weight range.
D) 30-35: This range falls within the obese category, indicating excessive body fat and potential health risks.

**Clinical Pearl:**
It is essential for healthcare professionals to assess an individual's BMI to understand their weight status and develop appropriate health recommendations. Regular monitoring of BMI can help prevent obesity-related health complications, such as cardiovascular diseases, diabetes, and certain types of cancer.

**Correct Answer:**
C. 18.5-24.9