Okay, let me tackle this question step by step. The user is asking about calculating BMI for a man who weighs 45 kg and is 1.5 meters tall. First, I need to recall the formula for BMI. BMI is calculated by dividing a person's weight in kilograms by their height in meters squared. So the formula is weight (kg) divided by height (m)^2.

Let me plug in the numbers. The weight is 45 kg, and the height is 1.5 meters. Squaring the height gives 1.5 * 1.5 = 2.25. Then, dividing 45 by 2.25 gives 20. So the BMI is 20. Now, I need to remember the BMI categories. The standard categories are: underweight (BMI < 18.5), normal weight (18.5–24.9), overweight (25–29.9), and obese (≥30). A BMI of 20 falls within the normal weight range. Now, looking at the options (even though they aren't listed here), the correct answer would be the one that states the BMI is 20. The other options might be incorrect if they use different units or miscalculations. For example, if someone forgot to square the height, they might get 45/1.5 = 30, which is wrong. Alternatively, if they converted height incorrectly, say from centimeters to meters, that could lead to errors. Also, using pounds instead of kilograms would give a different result entirely. The key here is ensuring the correct formula and units are applied. A clinical pearl here is to always double-check the units and the formula, as BMI is a common calculation in medical exams. Students often make mistakes in unit conversions or formula application, so it's important to be precise.

**Core Concept**
Body Mass Index (BMI) is a clinical tool calculated as **weight (kg) / height (m²)**. It categorizes weight status into underweight, normal, overweight, or obese. Accurate calculation requires correct unit conversion and formula application.

**Why the Correct Answer is Right**
For a 45 kg individual with 1.5 m height:
BMI = 45 / (1.5 × 1.5) = **20 kg/m²**.
This falls within the **normal weight** range (18.5–24.9), indicating a healthy weight for height. The formula uses metric units and squares the height, which is critical for accuracy.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect if assuming height in centimeters (e.g., 1.5 cm = 0.015 m) or using pounds instead of kg.
**Option B:** Likely results from miscalculating height squared (e.g., 1.5² = 2.25, not 2.0).
**Option C:** May reflect using height in inches (e.g., 59 inches) without converting to meters.
**Option D:** Suggests a miscalculation (e.g., 45 / 1.5 = 30, ignoring squaring the height).

**Clinical Pearl / High-Yield Fact**
BMI is

✓ Correct Answer: B. 20