**Core Concept**
The oxygen dissociation curve (ODC) illustrates the relationship between oxygen saturation and partial pressure of oxygen (PaO₂). Right shifting of the curve indicates decreased oxygen affinity of hemoglobin, facilitating oxygen release to tissues. Factors such as increased temperature, elevated CO₂, decreased pH, and increased 2,3-DPG promote this shift.

**Why the Correct Answer is Right**
Hypocapnia (low CO₂) leads to **alkalosis**, which increases blood pH and reduces hemoglobin’s affinity for oxygen, thereby **left-shifting** the O₂ dissociation curve. In contrast, hypoxia, increased temperature, and elevated 2,3-DPG all cause right shifts by promoting oxygen unloading. Thus, hypocapnia does not cause right shifting — it opposes it.

**Why Each Wrong Option is Incorrect**
Option A: Hypoxia causes right shifting by lowering oxygen saturation, which shifts the curve to the right via reduced O₂ affinity.
Option C: Increased temperature reduces hemoglobin-oxygen affinity by disrupting H-bonds in oxyhemoglobin, promoting right shift.
Option D: 2,3-DPG increases in anaerobic conditions and directly reduces hemoglobin’s oxygen affinity, shifting the curve to the right.

**Clinical Pearl / High-Yield Fact**
Remember: **"CO₂, heat, acidosis, and 2,3-DPG → right shift"**. Hypocapnia (low CO₂) is the exception — it causes alkalosis and a left shift. This is critical in conditions like hyperventilation, where patients may have low PaCO₂ and reduced O₂ delivery.

✓ Correct Answer: B. Hypocapnia