**Core Concept**
Immunoglobulin (Ig) changes in the variable region refer to the process of somatic hypermutation and class switching, which occur during the immune response to produce antibodies with high affinity for specific antigens.

**Why the Correct Answer is Right**
During the immune response, activated B cells undergo somatic hypermutation in the variable region of their immunoglobulin genes, resulting in increased affinity for the antigen. This process involves the introduction of point mutations in the variable region, leading to a higher affinity for the antigen. Class switching, on the other hand, involves the rearrangement of the heavy chain constant region to produce different classes of immunoglobulins (e.g., IgG, IgA, IgE).

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the changes that occur in the variable region of immunoglobulins.
* **Option B:** This option is incorrect because it refers to the process of clonal deletion, which occurs in the thymus and involves the elimination of self-reactive T cells, not changes in the variable region of immunoglobulins.
* **Option C:** This option is incorrect because it refers to the process of receptor editing, which involves the recombination of V, D, and J gene segments to generate new antigen receptors, not changes in the variable region of immunoglobulins.

**Clinical Pearl / High-Yield Fact**
Somatic hypermutation and class switching are critical processes that occur during the immune response, allowing the production of antibodies with high affinity for specific antigens. This process is essential for the development of immune memory and the production of protective antibodies.

**Correct Answer: B. Class switching.**