**Core Concept**
Total body water (TBW) is the total amount of water present in the human body. It is a critical parameter in understanding fluid balance and electrolyte homeostasis. The percentage of TBW varies with age, with infants having a higher percentage of body water compared to adults.

**Why the Correct Answer is Right**
In newborns, the percentage of total body water is approximately 70-80% due to a higher water content in tissues and organs. This high water content is essential for the rapid growth and development of the infant. The high percentage of body water in newborns is due to the high water content in the extracellular fluid compartment, which makes up a larger proportion of their total body water compared to adults.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately reflect the percentage of total body water in newborns.
**Option B:** This option is incorrect as it is too low and does not account for the high water content in newborn tissues and organs.
**Option C:** This option is incorrect as it is too high and does not accurately reflect the percentage of total body water in newborns.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the percentage of total body water decreases with age, and by the age of 60, it decreases to approximately 45-50%. This knowledge is crucial in understanding fluid balance and electrolyte homeostasis in different age groups.

**Correct Answer: D. 70-80%**