**Core Concept**
Oxygen affinity refers to the binding capacity of hemoglobin to oxygen. It is crucial for the delivery of oxygen to tissues. The affinity of hemoglobin for oxygen is determined by various factors, including pH, temperature, and the presence of 2,3-bisphosphoglycerate (2,3-BPG).

**Why the Correct Answer is Right**
Hypoxia, or a decrease in oxygen availability, actually decreases the affinity of hemoglobin for oxygen. This is known as the Bohr effect, where a decrease in oxygen tension (hypoxia) increases the release of oxygen to tissues. The Bohr effect is mediated by the decrease in pH, which increases the affinity of hemoglobin for 2,3-BPG. The binding of 2,3-BPG to hemoglobin reduces the oxygen affinity, facilitating the release of oxygen to tissues. Therefore, hypoxia does not increase oxygen affinity but rather decreases it.

**Why Each Wrong Option is Incorrect**
**Option A:** Alkalosis, or an increase in pH, decreases the affinity of hemoglobin for oxygen. This is the opposite of what occurs during acidosis, where the affinity for oxygen is increased.

**Option C:** Increased HbF, or fetal hemoglobin, has a higher affinity for oxygen compared to adult hemoglobin (HbA). This is essential for the delivery of oxygen to the fetus from the mother's bloodstream.

**Option D:** Hypothermia, or a decrease in body temperature, increases the affinity of hemoglobin for oxygen. This is due to the decrease in the rate of chemical reactions, including those involved in the binding and release of oxygen from hemoglobin.

**Clinical Pearl / High-Yield Fact**
The Bohr effect is a critical adaptation mechanism that ensures the delivery of oxygen to tissues under hypoxic conditions. It is essential to understand the effects of pH, temperature, and 2,3-BPG on oxygen affinity for effective management of respiratory and cardiac conditions.

**✓ Correct Answer: B. Hypoxia**