## **Core Concept**
The pH of blood is a tightly regulated parameter that reflects the balance between acidic and basic components in the body. It is crucial for maintaining proper physiological functions, including enzyme activity, protein structure, and cellular functions. The normal pH range of blood is slightly alkaline.

## **Why the Correct Answer is Right**
The correct answer, , reflects the narrow and slightly alkaline pH range of blood. This range is maintained by buffer systems, respiratory control of CO2 levels through the lungs, and renal control of bicarbonate and ion levels. The buffer system, which includes bicarbonate, phosphate, and protein buffers, helps to resist changes in pH. The respiratory and renal systems then work to correct any imbalances. A pH of 7.35-7.45 allows for optimal physiological function.

## **Why Each Wrong Option is Incorrect**
* **Option A:** This range is too acidic for normal blood pH and would indicate acidosis, a condition that can lead to serious complications if not corrected.
* **Option B:** Although closer, this upper limit is slightly below the normal range, and the lower limit extends into the acidic range, making it incorrect.
* **Option D:** This range extends into the acidic and is slightly too alkaline, making it broader and not reflective of the tightly regulated normal blood pH.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the body maintains blood pH within a narrow range. Slight deviations can indicate significant issues, such as respiratory or metabolic acidosis or alkalosis. The Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]), is crucial for understanding acid-base balance, particularly for bicarbonate buffering: pH = 6.1 + log([HCO3-]/[CO2]).

**Correct Answer: C. **