## Core Concept
The percentage of water in an adult human being varies based on factors such as age, sex, and body composition. However, on average, the human body is primarily composed of water.

## Why the Correct Answer is Right
The correct answer, , indicates that approximately 55-60% of an adult human's body weight is water. This percentage can fluctuate due to differences in muscle and fat content, with muscle having a higher water content than fat. The average distribution is roughly 60% for men and 55% for women.

## Why Each Wrong Option is Incorrect
* **Option A:** is too low for the average adult human body water percentage.
* **Option B:** is slightly below the generally accepted range.
* **Option D:** exceeds the typical upper limit for adult human body water percentage.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the percentage of body water decreases with age and increases with muscle mass. This fact can be crucial in various clinical settings, such as calculating drug dosages or understanding fluid balance.

**Correct Answer: B. **