**Question:** The amount of body water in human body is

A. 60%
B. 70%
C. 50%
D. 75%

**Correct Answer:** B. 70%

**Core Concept:** Water in the human body plays a crucial role in various physiological processes, and its distribution can vary depending on factors like age, body composition, and overall health.

**Why the Correct Answer is Right:** In adults, the proportion of body weight that is water is typically around 70%. This percentage is derived from total body water (TBW), which is approximately 40-50% of body weight. The remaining 30-50% of body weight is composed of fat, muscle, and bone.

**Why Each Wrong Option is Incorrect:**

A. 60%: This percentage is too low, as it falls below the typical range for adult body water proportion.

C. 50%: This percentage is too high, as it exceeds the typical range for adult body water proportion.

D. 75%: This percentage is too high, similar to option C, and the correct answer (70%) is the more accurate estimate.

**Why the Correct Answer is Right:** The correct answer (70%) is derived from the fact that approximately 60% of TBW is composed of plasma, and the remaining 40% is distributed among extracellular fluid (ECF) and intracellular fluid (ICF).

**Why Each Wrong Option is Incorrect:**

A. 60%: This percentage is too low, as it only accounts for plasma water, not the entire TBW.

C. 40%: This percentage is too low, as it falls below the range of 40-50% for ECF and ICF combined.

D. 50%: This percentage is too high, as it exceeds the range of 40-50% for ECF and ICF combined.

**Clinical Pearls:**

1. **Body Water Distribution**: Understanding the distribution of body water is essential for clinical practice, as it impacts electrolyte balance, blood volume, and overall body fluid homeostasis.
2. **Hydration**: Maintaining an adequate water balance is crucial for preventing complications such as dehydration or overhydration.
3. **Fluid Intake and Output**: Adequate fluid intake and balanced fluid output are crucial for maintaining normal body water balance.

4. **Fluid and Electrolyte Balance**: The distribution of body water affects electrolyte balance and overall fluid homeostasis. Understanding this concept will help in clinical practice, especially in managing patients with altered fluid and electrolyte balance (e.g., in critically ill patients or those on diuretic medications).