## **Core Concept**
The question tests understanding of thalassemia trait and its effect on hemoglobin A2 (Hb A2) levels. Thalassemia trait, also known as beta-thalassemia minor, is a genetic disorder characterized by reduced production of the beta-globin chains of hemoglobin. This condition often results in an increase in the production of other types of hemoglobin.

## **Why the Correct Answer is Right**
In beta-thalassemia minor, or thalassemia trait, there's a compensatory increase in the production of delta chains, which combine with alpha chains to form **Hb A2**. Normally, Hb A2 constitutes about 2-3.5% of the total hemoglobin in adults. However, in individuals with beta-thalassemia minor, the level of **Hb A2** is typically elevated, often above 3.5%, commonly ranging from 4% to 8%. This increase is a diagnostic marker for the condition.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests a decrease in Hb A2 levels, which is not characteristic of thalassemia trait. Decreased Hb A2 levels are not typically associated with this condition.
- **Option B:** This option implies a normal level of Hb A2, which does not align with the expected increase in Hb A2 levels seen in thalassemia trait.
- **Option D:** This option suggests a very high level of Hb A2, which, while possible, is not the most commonly accepted range for thalassemia trait.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that an elevated **Hb A2 level (>3.5%)** is a diagnostic criterion for beta-thalassemia minor. This fact is crucial for distinguishing it from other microcytic anemias, such as iron deficiency anemia, where Hb A2 levels are typically normal or decreased.

## **Correct Answer:** C. Increased.