**Core Concept**
2, 3 bisphosphoglycerate (2,3-BPG) is an organic phosphate compound found in red blood cells (RBCs), which plays a crucial role in regulating oxygen delivery to tissues. It does so by binding to hemoglobin and shifting its oxygen dissociation curve to the right, facilitating the release of oxygen to tissues with low oxygen levels.

**Why the Correct Answer is Right**
2,3-BPG binds to the beta chains of deoxyhemoglobin, causing a conformational change that reduces the affinity of hemoglobin for oxygen. This results in a decrease in the oxygen binding capacity of hemoglobin and an increase in the release of oxygen to tissues. The production of 2,3-BPG is stimulated by conditions such as high altitude, anemia, and increased metabolic rate, which require increased oxygen delivery to tissues.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because 2,3-BPG does not play a major role in regulating the pH of RBCs. While it does affect the oxygen binding capacity of hemoglobin, it does not directly influence the pH of the cell.

**Option B:** This option is incorrect because 2,3-BPG is not a major regulator of the glycolytic pathway in RBCs. While it is a byproduct of glycolysis, it does not directly regulate the rate of glycolysis.

**Option C:** This option is incorrect because 2,3-BPG does not play a major role in the regulation of calcium levels in RBCs. While it does affect the oxygen binding capacity of hemoglobin, it does not directly influence calcium levels.

**Clinical Pearl / High-Yield Fact**
The Bohr effect, which describes the decrease in oxygen affinity of hemoglobin in response to increased CO2 and decreased pH, is closely linked to the role of 2,3-BPG in RBCs. This relationship is often remembered using the mnemonic "2,3-BPG + CO2 = pH effect".

**Correct Answer:** B.